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186 Cards in this Set
- Front
- Back
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What is the nervous system?
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A "wired system"
- specific structural arrangement between neurons and their target cells; structural continuity in the system |
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What is the endocrine system?
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- a "wireless" system
- endocrine glands are widely disbursed and not structurally related to one another or their target cells? |
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Types of chemical messenger in each system?
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- the nervous system uses neurotransmitters that are released into the synaptic cleft
- the endocrine system uses hormones released into the blood |
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What are the distance of action of chemical messengers in the nervous and endocrine system?
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- the nervous system- chemical messengers travel very short distances (diffuse across synaptic cleft)
- the endocrine system's chemical messenders travel long distances (carried by the blood) |
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What are the means of specificity of action on target cell?
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Nervous system- dependent on close anatomic relationship between nerve cells and their target cells
Endocrine system- dependent on specificty of target cell binding and responsiveness to a particular hormone |
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What is the speed of the response? Nervous and Endocrine system?
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Nervous- rapid (milliseconds)
Endocrine- slow (minutes to begin) |
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What is the duration of the action? Nervous and Endocrine?
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Nervous- bried (milliseconds)
Endocrine- long (minutes to days or longer) |
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What is the major function of the nervous and endocrine system?
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Nervous- coordinates rapid, precise responses
Endocrine- controls activites that require long duration rather than speed |
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Do hormones from the Endocrine system have one receptor
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No! Hormones may have many receptors in different places
Example: Vasopressin in the heart and ADH in the renal system |
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Hormones?
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in circulatory system that when it is turned off it is eliminated or metabolized
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Central Nervous System
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Consists of the brain and spinal cord
- recieves input from the periphery (afferent division) - Output from CNS to peripher through the efferent division |
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Afferent Division
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Carries messenges away from the body to the CNS
- consists of sensory and visceral stimulation |
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Efferent Division
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Consists of the SOmatic and Autonomic Nervous system
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Somatic Nervous system
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- We are consciously aware of this stimuli (5 senses)
- Consists of motor neurons that affect skeletal muscle |
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Visceral Stimuli
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Part of the Afferent Devision of the Peripheral Nervous system
- Comes from the organs- BP, osmolarity of plasma, contents of stomach |
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Peripheral Nervous System
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Consists of the Afferent and Efferent Division
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Autonomic Nervous System
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- Consists of the sympathetic and parasympathetic nervous system
- both of theses systems affect smooth and cardiac muscle and glands - Ex: Baro Reflex- BP- Efferent command is an increase in heart rate because of a slight drop in BP when we go from sitting to standing - This is a sympathetic response??? |
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Nervous Tissue
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Along with muscle cells, neurons are known as excitable cells
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Neuronal cells
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- contain a cell body with a nucleus, a dentritic tree (Which receives signals via the dendrites), an axon (with an axon terminal that stimulates another cell)
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Membrane Potential
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Voltage difference across the membrane
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What can be found inside the cell that might have an effect on membrane potential?
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- Amino acids and proteins contribute to a net negative charge inside the cell
- The resting potential inside a cell is -70mV - Potassium is inside the cell and Sodium is outside the cell |
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Hydrophyllic
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dissolves in Water- Water is polar and therefore substances that dissolve in water are also polar
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Nonpolar substances dissolve?
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When in a lipid environment
- To diffuse across the plasma membrane it must be lipid soluble |
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How do substances diffuse across the plasma membrane?
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-Na and K cross through channels (proteins)
- These ions have a strong concentration gradient |
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What is the ionic basis for membrane potential?
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- ions are influenced by both a chemical and electrical gradient
- All ions want to reach a state of equilibrium - Equilibrium occurs when the plasma membrane is at a particular voltage called the equilibrium potential |
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Equilibrium
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No net driving force= no net movement
-The concentration gradient= the electrical gradient |
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Equilibrium Potential
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the voltage where an ion's electrical gradient balances out it's chemical gradient
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What happens in a cell as far as the ion gradient with K and Na?
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- At first Potassium's concentration gradient is stronger than sodium
- The voltage gated channels for potassium opens and as K leaves the cell the concentration gradient decreases and the electrical gradient increases-- Eventually there is equilibrium for K - The cell went from -70mV to -90mV - Na is permeable and enters teh cell- membrane potential becomes more positive (+60mV) - Eventually the chemical and electric gradient equal each other |
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Compare ICF to ECF in terms of ion concentration
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ICF--> K+, Mg++, proteins
ECF --> Na+, Ca++, Cl-, HCO3- - There are some of each ion in and out of the cell- I put the ion in a category based on the greater concentration of that ion |
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What is the ionic basis for membrane potential?
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1) the ions present and their individual equilibrium potentials and 2) the relative permeability of the membrane to each ion
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At resting membrane potential what ion is most near to equilibrium?
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_ Potassium- Resting membrane is closer to -90mV
- It is actually -70mV - However Sodium has a higher driving force via leak channels for a cell at rest |
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What is the equilibrium potential compared to the resting membrane potential for Na & K?
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For Sodium the equilibrium potential is +60mV and for Potassium the equilibrium potential is -90mV
- Since the resting membrane potential of the cell is -70mV Potassium is closer to equilibrium and Sodium has a greater driving force - Leak channels allow for the influx of Sodium |
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What happens at the axon hillock?
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- As information is integrated at the axon hillock, depolarization or hyperpolarization may occur-
- Inhibitory inputs call hyperpolarization making the cell more negative - Depolarization is caused by excitatory inputs that makes the cell less negative - If the axon hillock is depolarized to the threshold value (ranges from -55mV to -40mV) an action potential will be triggered |
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How is an action potential executed?
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Ion channels in the membrane open in response to the depolarization
- Since they respond to voltage, they are known as voltage gated ion channels 1) The Na+ channels respond to the depolarization- Sodium moves into the cell which makes the cell more positive- Sodium channels rapidly close when teh membrane potential reaches about +35mV - The now positive potential inside the cell triggers for the voltage gated potassium channels to open and potassium is driven out of the cell - The movement of positive charges out of the cell will result in restoration of the negative membrane potential (repolarization) - Often too much K+ exits the celland the membrane becomes more negative than resting membrane potential (Hyperpolarization) |
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What ion wants to go where in the cell
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Sodium wants to go in the cell because it is more negative inside (electrical gradient) and there is less sodium inside (Chemical gradient)
- There is a strong electric and chemical gradient for sodium to move into the cell |
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Excitatory and inhibitory input?
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Excitatory- depolarizes the cell which moves the membrane potential closer to threshold
Inhibitory- repolarizes the cell which moves it away from threshold |
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What is myelin?
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Myelin is an insulator- prevents the loss of the electrical signal- speeds up the rate of conduction because the signal hops from node to node (saltatory conduction)
- Myelin is produced by oligodendrocytes in the CNS and Schwann cells in the PNS |
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Nodes of Ranvier
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small breaks in the myelin sheath at regular intervals along the axon membran- they are critical to proper signal conduction
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Glial Cells-
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Non-neuronal cells in the CNS that provide support
- Astrocytes- intricate part of the blood brain barrier- also very good at cleaning up the brains ECF which controls the excitability of the brain - oligodendrocytes - Ependymal Cells- epithelial cell that lines the central ventricles |
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Sensory/Motor
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Sensory input goes through afferent pathways to the brain
Motor input goes through efferent pathways to the body or effector organs |
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Interneurons
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communicate between afferent and efferent neurons- these are only involeved in local circuits
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Afferent Neurons
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Neurons that carry information from the periphery to the brain or spinal cord
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Efferent Neurons
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neurons that carry information from the brain or spinal cord to the periphery
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How are neurons organized?
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Either in aggregates (nuclei, ganglia) or elongated columns or layers- forms functional units
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Somatotopic Arrangements
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map of cells in the brain such as the primary motor and somatosensory cortex
Motor cortex- every voluntary movement Sensory cortex- every somatic sensation is percieved here |
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CSF
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fluid filled spaces of the brain
- cells within the brain are only exposed to CSF or brain extracellular fluid- this is a result of filtering blood and plasma through the blood brain barrier - CSF is produced in teh choroid plexus which is a highly vascularized structure where plasma is converted into CSF - CSF immediately enters the ventricular system and spinal cord's central canal - the 4th ventricle allows CSF to exit to subarachnoid space --> arachnoid space --> superior saggital sinus --> circulatory sytem - production and removal of CSF helps maintain optimal intracranial pressure |
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Meninges layers
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Dura Mater- outermost
Arachnoid Mater Subarachnoid Space- vascularly high Pia Mater |
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Superior Sagittal Sinus
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important part of the circulatory system- production and removal of CSF to maintain value optimal for intracranial pressure
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How is CSF different than plasma?
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1) There is a difference in ion concentration and proteins
2) Plasma has a higher concentration of sodium 3) CSF has a lower concentration of Sodium- this reduces excitability 4) CSF has higher extracellular Potassium to keep cell membrane more negative 5) In brain amino acids and proteins are often neurotrasnmitters so it is important to control the amount available 6) Look at chart |
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Blood Brain Barrier (BBB)
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- Physical structure that protects the brain from elements within the blood
- ultrafilters plasma - Composed of 3 different barriers: 1) Capillary Wall- in brain there are tight junctions (in other parts of the body there are pores) to get through the capillary a substance must cross endothelial cells that line the capillary with a plasma membrane (lipid soluble substances can readily cross the membrane) (steroid hormones can cross blood brain barrier (estrogen, testosterone, progesterone) - water soluble substances need a transporter (glucose for example) 2) Basement membrane- composed of glycoproteins (proteins with glucose groups attached) 3) End foot processes of Astrocytes- |
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Circumventricular organs
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There are certain parts of the brain that it is okay to be leaky
- these parts are exposed to plasma more than the rest of the brain - located around the ventricles specifically the 3rd, later, and 4rth ventricle - Posterior pituitary, OVLT, subfornical organ, pineal gland, area postrema, subcommisural organ - advantage is to allow the brain to be exposed in a controlled way to plasma while protecting the brain - the brain can see and react to whats going on in circulation - can react to protein/amino acid based hormones that cant cross BBB, fluctuations in osmolarity - initiate responses to correct problems - sensitive to cytokines |
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OVLT and Subfornical Organ
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- Highly sensitive to changes in plasma osmolarity
- Will release ADH to adjust water levels of plasma to correct problems with osmolarity |
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Cytokines
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- proteins released by immune system that may stimulate fever
- proteins that cannot cross the blood brain barrier |
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Neuronal Communication
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- cells stimulate or inhibit each other in a junction point called a synapse
- This occurs via electrical and chemical synapses - most cells' language is action potentials - rare cells communicate via graded depolarizations |
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Electrical Synapse
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- The action potential or depolarization simply diffuses across a large ion channel into the adjacent cell
- the large ion channel is called a gap junction - direct flow of depolarization from one cell to the next |
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Chemical Synapse
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- the release of a neurotransmitter and the binding of that neurotransmitter to the next cell
- more complex and common - the electrical signal is converted into a chemical signal (neurotransmitter) then converted again to an electrical signal |
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Types of Neurotransmitters
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- Amino Acid
- Monoamine- derived from an amino acid - Catecholamine- type of monoamine that is rerived from tyrosine - Neuro active peptides (not neurotransmitter) is co-released with neurotransmitter and affects the second cells response |
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Neuromuscular Junction
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- the synapse between motor neurons and skeletal muscle
- easy to study (large synapse and common) - can physically see the result of stimulation (muscle twitch) - the basic events of other chemical synapses are the same |
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Chemical Synapse (NMJ)
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- The neurotransmitter used is acetylcholine and it is bound to receptors on the 2nd cell
- Presynaptic cell --> synaptic cleft --> Postsynaptic cell - vesicles of neurotransmitter is being synthesized and packaged in the cell body and shuttled down the axon and housed in the terminal Electric signal --> Chemical --> Electrical |
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How does the chemical synapse work?
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- Action potential travels down the axon and penetrates the terminal, which depolarizes the terminal
- When the terminal depolarizes K+ moves out of the cell- it triggers the opening of a voltage gated ion channel for Calcium - Calcium enters the terminal and facilitates vesicles of neurotransmitter to exocytose into the terminal membrane - vesicles of neurotransmitter (acetylcholine) gets dumped into synaptic cleft - The acetylcholine diffuses across the cleft and binds to the receptor on the postsynaptic cell - The postsynaptic cell ion channels open and sodium enters the post synaptic cell (further depolarization) - eventually the skeletal muscle will contract - if the neurotransmitter is excitatory it will depolarize the cell, but if it is inhibitory it will hyperpolarize the cell (Potassium could be opened to hyperpolarize, or chloride could enter to hyperpolarize) |
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Exocytosis
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vesicles fuse with the plasma membrane and the contents of the vesicles gets dumped into the ECF
- calcium dependent process |
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Neurotransmitter Categories-
Amino Acid neurotransmitters |
- these neuronal cells in the brain are using neurotransmitters that can be used for energy or structure (efficient system)
- Glutamic acid/ glutamine- all purpose excitatory neurotransmitter in the brain - GABA-all purpose inhibitory neurotransmitter in the brain - Glycine- all purpose inhibitory neurotransmitter in the brain |
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Neurotransmitter Categories-
Monoamines |
- derived from amino acids but the amino acid has undergone a modification in structure
- acetylcholine, serotonin, histamine |
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Neurotransmitter Categories-
Catecholines |
derived from tyrosine
- dopamine, epinephrine, norephinephrine |
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Neuroactive peptides
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chains of amino acids (peptides) that are found in the brain and are usually colocalized with various neurotransmitters
- performing neuromodulations- adjusting the effects neurotransmitters have on post synaptic cells - potentiating the effect- increase or decrease sensitivity - arginine/ vasopressin/ adh- co-released and performs neuromodulation |
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Pattern of Synaptic Connectivity
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Comes in two basic forms:
1)Spatially focused- one cell or a group of cells synapse onto 1 to a few postsynaptic cells - follows a direct line - used by simple circuits for simple commands 2) Widely Divergent- 1 or a few neurons make many brances and synapse onto a huge number of targets- this allows a small group of neurons to affect the general excitably of a large number of targets - influences more complex behaviors like mood, sleep/wake cycle, attention span- are not located in one part of the brain- many different parts of the brain acts together |
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Widely Divergent pattern of connectivity example
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- these neurotransmitter systems are often manipulated when people take drugs that have targets in the brain such as antidepressants, drugs that correct ADD
- affect neurotransmitter systems that have a widely divergent pattern Example 1: The norepinephrine system originates in the locus coeruleus, which extends into the cerebellum, cerebral cortex (higher order executive function), hippocampus (memories), amygdala (triggered during visceral fear reactions, hypothalamus (basic life sustaining functions) - norepinephrine influences all these places- influences sleep/wake cycle, mood, and attention - later generation antidepressants, adult ADD interact with norepinephrine system |
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Serotonin
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- originate in nuclear aggregates called the Raphe nuclei
- best known for it's affect on mood/ happiness/ sense of well being - has several targets in hypothalamus (affects temp regulations), cerebellum, basal ganglia - drugs like antidepressants, ecstasy - euphoria- vulnerable to dehydration because temperature rises |
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Dopamine
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originates in two different parts of the brain (widely divergent but not as much as the other systems, a little more specific)
1) Substantia Nigra- projects to portions of the basal ganglia and affects motor movements (Parkinson's- dopamine deficiency in substantia nigra cells) 2) Ventral tegmental area- projects to prefrontal cortex- the reward system! (lab animals press lever all day) |
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Acetylcholine System
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- mysterious mess!
- originates from three different places (septal nuclei, nucleus basalis, pontomesencephalotegmental complex) and projects everywhere - affects sleep/wake cycle and potentially attention |
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Gap Junction
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ion channels that span the distance between the presynaptic and postsynaptic cell- electrical synapse
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Electrical synapse
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- important during electrical coupling of cells
- uses gap junctions - cardiac muscle cells - heart contracts as a unit |
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Parts of the brain
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brainstem, cerebellum, basal ganglia, cerebral cortex, hypothalamus
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Brainstem
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- lower portion of the brain before the spinal cord made up of the medulla, the pons, and the midbrain
- maintenance of basic vegetative functions - maintains and controls respiration, cardiovascular function - can lose function of the rest of teh brain but the brainstem is still functioning you will be alive - oldest part of the brain evolutionary |
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Cerebellum
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- involved in the regulation of motor movements
- especially learned motor movements - structure that houses our motor patterns (a motor movement that we have learned to do and now do automatically (signing your name) |
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Basal Nuclei/ ganglia
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also involved in motor movement
- involved in purposeful motor movement - fine movements - prunes motor movements (removes excess) - Parkinson's- loss of dopamine cells in basal ganglia- gets worse when someone is trying to make a movement |
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Cerebral Cortex
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- contains primary motor cortex- initiation of voluntary movement
- all higher order brain functions arise, like voluntary motor movements, executive functions (regulating attention), visual processing, the perception of perceiving input from the outside world (vision, olfactory, hearing input) |
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Hypothalamus
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regulates basic vegetative functions
- beyond our conscious awareness - regulation of body temperature, appetite, feeding, water balance in the body - association with the pituitary gland (endocrine system) |
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Lobes of the Brain
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- named after the parts of the skull that lay on top of them
- frontal, parietal, temporal, occipital |
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Frontal Lobe
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-important in determination of personality
- Finneus Gage- railroad worker |
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Occipital Lobe
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- primary visual cortex- all visual information is percieved
- the visual information from the retinas are sent by the optic nerve to the occipital lobe - make meaning of the visual information |
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PNS
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- extending out from the CNS from the brain in spinal cord is the PNS
- the part that extends out from brain is the cranial nerves and the part that extends out from the spine are called the spinal nerves |
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Cranial Nerves
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- There are twelve pairs of them
- Oh Oh Oh To Touch And Feel Virgin Girls Vaginas And Hymens - Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, Acessory, Hypoglossal |
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Cranial Nerves
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- the majority of them branch out from the brainstem with the exception of the first couple
- Some are sensory, some are motor, and some are both |
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Cranial Nerves: Sensory, Motor, or Both?
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Some Say Marry Money, But My Brother Says Big Brains Matter Most
1 - Olfactory - S ome 2 - Optic - S ay 3 - Oculomotor - M arry 4 - Trochlear - M oney 5 - Trigeminal - B ut 6 - Abducens - M y 7 - Facial - B rother 8 - Vest/Coch - S ays 9 - Glossopharyngeal - B ig 10 - Vagus - B rains 11 - Accessory - M atter 12 - Hypoglossal - M ost |
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Vagus Nerve
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Afferent and Efferent fibers- autonomic nerve- most important component of the parasympathetic nervous system
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What cranial nerves are part of the parasympathetic nervous system?
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3- Oculomotor
7- Facial 9- Glossopharyngeal 10- Vagus |
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Spinal Nerves
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- extend out from the spinal cord
- there are 31 pairs - every single spinal nerve with the exception of C1 are both sensory and motor |
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Spinal Cord
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- layers of meninges
- contains white and gray matter - root fibers that come out of a ventral and dorsal surface that merge to form a spinal nerve - Ventral- efferent fibers (motor) - Dorsal- afferent fibers (sensory) |
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Ventral Roots
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Contains motor fibers that come out of the spinal cord that will ultimately innervate skeletal muscle
- the direction is out |
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Dorsal Roots
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Contains sensory fibers that are coming from the body (skin, muscle) and are conveying sensory information into the spinal nerve
- the direction is in |
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Spinal nerve
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mixture of ventral and dorsal fibers
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Spinal Cord
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Cervical
Thoracic Lumbar Sacral |
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Dorsal Root Ganglia
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- swelling before the formation of the spinal nerve is where the cell bodies of the somatosensory nerves are located
- the sensory neuron does not match the basic neuronal structure- the cell body is distant from the receptor closer to the CNS |
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Dermatome & Myotome maps
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Dermatome- sensory maps
Myotome - motor maps |
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Spinal Cord
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White Matter- where axon fibers are concentrated (myelin makes them white!)
Grey Matter- where cell bodies are concentrated |
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White Matter
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- think vertically in the spinal cord
- the white matter contains axon tracks that move up and down from and to the brain - Up towards the brain- sensory fibers (afferent) (ascending tracts) - Down from the brain- motor fibers (efferent) (descending tracts) - most is on dorsal surface |
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Ascending tracts
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often called spinocerebellar or spinothalamic
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Descending tracts
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corticospinal
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Grey Matter
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divided into regions referred to as horns
Dorsal Horn- the sensory nerves are coming in and synapsing onto interneurons Lateral Horn Ventral Horn- |
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Gray Matter
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- we think about horizontally because these cell bodies are sitting in the spinal cord and there are sensory nerves coming for each level and motor neurons coming out to innervate different layers of muscle groups
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Lateral Horn
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- the autonomic nervous system
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Pure spinal reflex
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- is a motor pattern that does not require descending input from the brain
- involves sensory input coming in from the spinal cord and motor input coming out - example- patellar reflex! - will get a knee jerk if someone has a spinal cord injury above that level of spinal cord |
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Pain Withdrawal Reflex
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- right leg pain- Withdraw the limb- flex the knee- contract the hamstring and relax the quadricep
- contract the quadricep and relax the hamstring on the left side - The Sensory nerve comes in and synapses onto two interneurons - One interneuron stimulates the motor neurons that innervate the hamstring on the right side - the other interneuron- stimulates inhibition |
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Pain Withdrawal Reflex Interneurons
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- Interneuron is crossing over to the other side and enters the white matter to go to the brain
- the interneurons that cross over performs the opposite pattern on the left side - interneuron stimulates the motor neurons that innervate the hamstring on the right side - the other interneuron is inhibiting and resulting in relaxation of the quadricep |
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Painful Stimulus on right leg
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- Flex the knee- contracts the right hamstring and relax the quadricepperforms the opposite pattern on the left side
- interneuron stimulates the motor neurons that innervate the hamstring on the right side - the other interneuron is inhibiting and resulting in relaxation of the quadricep - On the left leg I need to relax the hamstring and contract the quadricep -the sensory nerve comes in and synapses onto two interneurons |
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Autonomic Nervous system
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the division of the nervous system that controls visceral function
- it includes visceral sensations that are coming into the spinal cord and up to the brain and efferent commands that innervates smooth, cardiac muscle and glandular tissue |
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Two arms of the autonomic nervous system
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Visceral stimulation- the sensory arm of the autonomic nervous system
- Efferent division- parasympathetic and sympathetic- the command arm of the autonomic nervous system |
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Efferent Division
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Sympathetic- stress like response
Parasympathetic- rest and digest |
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Sympathetic Nervous and Parasympathetic Nervous system
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anatomically both systems there are three basic cells
- preganglionic neuron --> postganglionic neuron --> target cell - 2 synapses |
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Ganglion
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collection of cell bodies and synapses
- arrangement is differenet in para and sympathetic nervous system - collection of cell bodies and synapses that occur outside of the CNS -Preganglionic neuron whose cell body is sitting in the spinal cord that projects out to a postganglionic neuron, which projects out to a target cell |
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Sympathetic Nervous System
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the arrangement is uniform
- the preganglionic neurons that these circuits start with that sit in the spinal cord-- > project out of the spinal cord and synapse onto the postganglionic cell, which sits in a peripheral ganglion - sympathetic peripheral ganglion is found in the sympathetic chain ganglion - the postganglionic neurons branch out from the chain to the target cells *** Some of the preganglionic neurons bypass the chain synapse at a ganglia outside of the chain (prevertebral ganglia- hypogastric plexus and celiac ganglion) |
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Preganglionic Cells
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- located in the lateral horn of the spinal cord
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Adrenal Medulla- endocrine arm of the sympathetic nervous system
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- the adrenal glands are endocrine glands that are sitting on top of eac kidney
- the inner portion of each adrenal gland is called the adrenal medulla - secrete epinephrine and norepinephrine - the preganglionic neurons innervate the adrenal medulla directly and can stimulate the release of epinephrine and norepinephrine into the bloodstream- endocrine arm of the sympathetic nervous system - advantage can be a rapid neuronal response and you can have a more delayed response (hormonal response) |
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Sympathetic Nervous SYstem- How does stimulation occur?
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- highly elaborate system
- when stimulated can stimulate a large number of targets all at once - global response- generally speaking you get this kind of response - the anatomy supports this global activation |
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Parasympathetic nervous system
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- anatomically very different from the sympathetic nervous system
- the preganglionic neurons are located in the brainstem and the sacral portions of the spinal cord- it extends out of the brainstem cranial nerve 3, 7, 9, and 10 - it extends from sacral nerves 2, 3, and 4 - the ganglia associated with this system are located near or on the target organ - the postganglionic fibers are short |
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Vagus Nerve
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cranial nerve 10 carries about 75 percent of the parasympathetic input to the body
- essential for parasympathetic input for the body |
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Neurotransmitters of the ANS
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1) Cholinergic- Acetylcholine
2) Adrenergic- Norepinephrine |
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Sympathetic Nervous System
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- The Preganglionic cell releases acetylcholine onto the postganglionic cell
- the receptor that acetylcholine binds to is called the nicotinic acetylcholine receptor - postganglionic cell releases norepinephrine onto an adrenergic receptor on the target cell |
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Parasympathetic Nervous System
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- the preganglionic cell releases acetylcholine onto the postganglionic cell
- the postganglionic neuron releases acetylcholine onto the muscarinic acetylcholine receptor on the target cell |
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If I applied a acetylcholine receptor agonist onto cells on the heart that controls heart rate
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- decreases heart rate
- a parasympathetic response because it stimulates the receptors that respond to the parasympathetic response |
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Adernergic Receptors
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Alpha 1- smooth muscle lining blood vessels- when epinephrine or norepinephrine binds to the smooth muscle it causes vasoconstriction- blood vessels that are perfusing viscera
Alpha 2 Beta 1- found on cardiac muscle- when stimulated they increase heart rate, contractility of the heart Beta 2- found in the lungs- found in the smooth muscle that lines the airways- when stimulated they cause relaxation of that smooth muscle (active ingredient in inhalers is epinephrine or agonist-- dilates airways) - the response is sympathetic! |
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Alpha Receptors
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- vasoconstriction
- Iris dilation - intestinal relaxation - Intestinal sphincter contraction - Bladder spincter contraction - Pilomotor contraction |
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Beta Receptor
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Beta 2 receptors are also found on the smooth muscle of blood vessels perfusing skeletal muscle- when stimualted dilation -- which increases blood flow to cardiac muscle
- Vasodilation - cardioacceleration- increase heart rate - Increased myocardial strength- contractility of heart - Intestinal relaxation - Bronchodilatation - Caloriogenesis - Glyogenolysis - Lipolysis - Bladder wall relaxation |
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SYmpathetic Innervation- no parasympathetic
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- kidneys
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Autonomic Tone
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this refers to the fact that for both systems there is a baseline input to nearly every target cell
- it is little like the volume of stimulation - when we shift from parasympatetic to sympathetic mode we are changing the baseline tone - parasympathetic is active the vast majority of the ton - parasympathetic tone is high - sympathetic tone is low - but when we mobilize a stress response we shift to increase sympathetic tone |
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The ANS Control Centers
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- the control of autonomic stimulation to the body is done by parts of teh brain
- autonomic control centers reside in the hypothalamus or parts of the brain stem - these centers are recieving visceral stimulation constantly and deciding what type of efferent response needs to occur |
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Endocrine system
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- second control system
- a hormone must be released directly into bloodstream - an endocrine gland releases a hormone directly into the circulatory system |
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Delayed response of endocrine system?
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- release of the hormone
- blood concentration needs to reach a point for something to happen - the hormone will be available to bind to receptors until it is eliminated |
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Endocrine Glands
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- central endocrine glands- endocrine glands located in the CNS- hypothalamus, pituitary gland, pineal gland
- peripheral endocrine glands- located in the body- parathyroid, thyroid, thymus glands, - Dedicated Endocrine glands- only function is to act as aendocrine gland- thyroid, parathyroid, adrenal glands - Mixed function glands- the heart, kidneys (releases erythropoietin) |
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Hormone Receptor Theory
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- the effect that a hormone has on a target cell depends on the receptor it binds to
- a hormone can have many types of effects that is mediated by many types of receptors - the relationship between the hormone and receptor determines the physiological response |
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What does the hormone binding on the target cell trigger?
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three basic intracellular repsonses:
1) Alters channel permeability by acting on pre-existing channel-forming proteins 2) Acts through a second-messenger system to alter activity of pre-existing proteins 3) Activates specific genes to cause formation of new proteins |
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1) Alters channel permeability by acting on pre-existing channel-forming proteins
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hormone binds to a receptor and opens a calcium channel, which leads to the release of secretory vesicles that contain hormone)-- physiological response is a release of hormone as a result of the opening of calcium channels
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Hormone binds to a target cell
2) Acts through a second-messenger system to alter activity of pre-existing proteins |
(intracellular signaling cascade- often lead to phosphorylation of a protein (adding or taking away a phosphate group-- turning on or off proteins)) Example- enzymes - insulin acts on a cell- insulin binds to a receptor and phosphorylates enzymes (insulin is released in times when glucose levels rise) glucose is stored in the form of glycogen
- insulin can activate enzymes that synthesize glycogen - it can also deactive enzymes |
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Hormones bind to a target cell
3) Activates specific genes to cause formation of new proteins |
- activating a gene increases the expression of some proteins
- inactivating a gene shuts off the formation of some proteins - one hormone could activate genes that code for the epinephrine receptor (adernergic receptors)- increases cell's sensitivty of epinephrine |
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Types of hormones
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1) Peptide and Protein Hormones
2) Amino Acid Derived Hormones 3) Steroid Hormones - the important distinction is solubility- water and lipid soluble hormones- effects how the hormone is synthesized, stored, transported inthe blood stream, and how it influences the target cell |
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Peptide and protein hormones
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chains of amino acids that are connected by peptide bonds (can be short or long)
- water soluble |
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Amino acid derived hormones
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a single amino acid has been modified in some way
- water soluble |
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Steroid Hormones
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derived from cholesterol
- lipid soluble |
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Water Soluble Hormones
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- synthesized as pro or prehormones that are longer that the active hormone
- it is inactive and activation involves cleavage steps - usually stored in intracellular vessicles - transported free in plasma - limited to binding to surface receptors on teh target cell's plasma membrane - if the receptor is located inside the cell- the hormone needs to use a secondary messenger system |
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Fat Soluble Hormones
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- synthesized by cholesterol
- not stored in intracellular vessicles because they diffuse out - they are often produced on demans and stored intracellularly bound to a protein that stays in the cell - found in circulation bound to plasma proteins - in order to have them available-- less of these plasma proteins are produced- the hormones unbind and act on target cells - the lipid soluble hormones can bind to albumin - there are also specific binding proteins for certain lipid soluble hormones- the affinity for this protein is higher so it spends more time bound- the purpose of these proteins is transport and storage - these fat soluble hormones can bind to intracellular receptors inside the nucleus- the receptors regulate gene expression and control the production of proteins |
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Albumin
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protein that binds to lipid soluble hormones
- multi purpose shuttle bus for all lipid soluble hormones |
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Thyroid hormone
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amino acid derives (derived from tyrosine)
- it is lipid soluble and nonpolar - exception to rule - behaves as a fat soluble hormone except it is not synthesized from cholesterol |
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Peptide hormone
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vasopressin & ADH- produced in the hypothalamus
- acts through a secondary messenger system |
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Amino acid derived hormones
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- derived from tyrosine
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Thyroid Hormone
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- thryoid hormone- T3 & T4 refers to the number of iodines attached to the structure
T3 is an active form of thyroid hormone T4 needs to be converted to T3 to be active the presence of iodides creates a nonpolar structure which is why they are lipid soluble |
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Peptide Hormone Syntehsis
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example of a pro or prehormone that becomes active
-Angiotensinogen - regulates plasma volume and BP in the renal system - Angiotensinogen is inactive and has a long structure-- two cleavage steps to become active - Angiotensin 2 has a variety of effects |
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Steroid Hormone Synthesis
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- derived from cholesterol
- two types of cholesterol (HDL & LDL) - LDL are essential in the body- primary way that cholesterol is transported through the bloodstream - cholesterol is needed by every cell in the body -- (in the plasma membrane- structural lipid) - cholesterol is required to produce steroid hormones - the uptake of LDL is precise- binds to LDL receptors and is internalized through receptor mediated endocytosis - the LDL is unpackaged to liberate teh cholesterol which is then used to produce steroid hormones |
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Action that Water soluble hormones perform are:
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- changing the permeability of the cell and acting through a second messenger system
- both of these actions are mediated through receptors on the plasma membrane - opening an ion channel means that the hormone is actually gating the ion channel - acting through a second messenger system involves the binding of that hormone to a surface receptor (G protein coupled receptors) |
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G proteins
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proteins that have attached GTP that is similar to ATP but with a guanine instead of adenosine-
- the breakdown of GTP releases energy required to activate a second messenger system |
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Second Messenger sytem
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the two second messenger are a rise in intracellular calcium or a rise in cyclic AMP levels
- both of these second messenger systems are associated with teh phosphorylation or dephosphorylation of proteins (turn on or off) - these proteins are often enzymes that catalyze reactions - the function of these enzymes dictate the cell's response-- a hormone can turn on or off a series of enzymes (Ex- insulin and glucagon) |
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Lipid soluble Hormones method of action
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- usually steroid hormones act on receptors in the nucleus
- the plasma membrane is not a barrier because they easily diffuse across the membranes - receptors are often found along segments of DNA- located at the promotor region of genes (they regulate the expression of genes) - the hormone will either turn on or off the gene- - if it turns it on the gene gets transcribed into mRNA and a new protein is formed |
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Peptide hormone
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vasopressin & ADH- produced in the hypothalamus
- acts through a secondary messenger system |
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Amino acid derived hormones
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- derived from tyrosine
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Thyroid Hormone
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- thryoid hormone- T3 & T4 refers to the number of iodines attached to the structure
T3 is an active form of thyroid hormone T4 needs to be converted to T3 to be active the presence of iodides creates a nonpolar structure which is why they are lipid soluble |
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Peptide Hormone Syntehsis
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example of a pro or prehormone that becomes active
-Angiotensinogen - regulates plasma volume and BP in the renal system - Angiotensinogen is inactive and has a long structure-- two cleavage steps to become active - Angiotensin 2 has a variety of effects |
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Steroid Hormone Synthesis
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- derived from cholesterol
- two types of cholesterol (HDL & LDL) - LDL are essential in the body- primary way that cholesterol is transported through the bloodstream - cholesterol is needed by every cell in the body -- (in the plasma membrane- structural lipid) - cholesterol is required to produce steroid hormones - the uptake of LDL is precise- binds to LDL receptors and is internalized through receptor mediated endocytosis - the LDL is unpackaged to liberate teh cholesterol which is then used to produce steroid hormones |
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Action that Water soluble hormones perform are:
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- changing the permeability of the cell and acting through a second messenger system
- both of these actions are mediated through receptors on the plasma membrane - opening an ion channel means that the hormone is actually gating the ion channel - acting through a second messenger system involves the binding of that hormone to a surface receptor (G protein coupled receptors) |
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G proteins
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proteins that have attached GTP that is similar to ATP but with a guanine instead of adenosine-
- the breakdown of GTP releases energy required to activate a second messenger system |
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Second Messenger sytem
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the two second messenger are a rise in intracellular calcium or a rise in cyclic AMP levels
- both of these second messenger systems are associated with teh phosphorylation or dephosphorylation of proteins (turn on or off) - these proteins are often enzymes that catalyze reactions - the function of these enzymes dictate the cell's response-- a hormone can turn on or off a series of enzymes (Ex- insulin and glucagon) |
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Lipid soluble Hormones method of action
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- usually steroid hormones act on receptors in the nucleus
- the plasma membrane is not a barrier because they easily diffuse across the membranes - receptors are often found along segments of DNA- located at the promotor region of genes (they regulate the expression of genes) - the hormone will either turn on or off the gene- - if it turns it on the gene gets transcribed into mRNA and a new protein is formed |
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Example of lipid soluble hormone method of action
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- one of the manyg enes that the thyroid hormone regulates is the epinephrine receptor
- when thyroid hormone binds to the receptor it increases the mRNA for that receptor and you get an increase in production of that receptor and the receptor goes to the plasma membrane and can bind to epinephrine more readily - thyroid hormone regulates general metaolic related processes - lipid soluble usually regulate a wide variety of genes |
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Exceptions to lipid soluble hormone's method of action
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there are examples of lipid soluble hormones that have receptors at the plasma membran or floating in the cytosol!
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Hormone binding proteins
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- hormones bind to plasma proteins in circulation
- all lipid soluble must bind to a plasma protein (albumin is the generic example) to be transported in circulatory system - specific binding proteins are produced to bind to a specific hormone- they bind to lipid and water soluble hormones |
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Purpose of hormone binding proteins
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1) Allows for transport of lipid soluble hormones
2) provides blood with a reservoir of hormone, minimizing minute to minute flunctuations in hormone concentration (we want the hormone level to be stable because hormones have long term effects- for example thyroid hormone levels determine BMR-- thyroid hormone binding protein makes the hormone unavailable to bind to cells) (growth hormone and IGF are water soluble that have binding proteins) 3) Extends the half life of the hormone in circulation- while the hormones are bound to plasma protein are not available to be eliminated so it extends their life |
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Hormones that bind to plasma proteins?
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- are ones whose action are more long term like those involved in inducing the synthesis of new proteins in target tissues
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Plasma Hormone Concentration
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A Hormone's effect is proportional to its plasma concentration
- Homeostatically controlled- via elaborate negative feedback control |
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Effects of Hormonal Secretion
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The free biologically active hormone go back and forth between binding and unbinding
- the relationship between a hormone and its binding protein is that it is always binding and unbinding - the higher affinity for the hormone to the plasma protein the more time is in the bound state - albumin has a low affinity for hormones |
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The concentration of the hormone in the blood depends on these factors:
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1) The Endocrine gland and how much it secretes
2) The amount that binds to target cells and provide a physiologic response 3) Metabolism in liver or other tissues 4) Removed from circulation through excretion in urine 5) Bound to plasma proteins |
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Plasma Concentration is not always a factor in the hormone's effect. What else effects the hormone's affect?
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1) Permissiveness
2) Complementary Actions 3) Synergism 4) Antagonism |
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Permissive relationships- hormones
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- the presence of one hormone is necessary in order for the target cell to adequately respond to a second hormone
- Example- relationship between cortisol and norepinephrine and epinephrine- a certain level of cortisol is necessary for the circulation to respond to epinephrine and norepinephrine (change in BP by constriction) |
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Complementary Actions- Hormones
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- certain hormones are paired together to create a physiological response- they have different affects but are complementary and necessary to function
- Example- the relationship between prolactin and oxytocin - Prolactin acts on mammary glands to produce mile - Oxytocin is necessary for the let down- release of the milk |
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Synergism
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Synergy is when two or more hormones/ chemical messengers are neeeded to produce an effect that is greater than the sum of their effects
- 1+1=3 Example- FSH and testosterone and their role in sperm production - adequate levels of both hormones are necessary for sperm production- each hormone has its own action but when both come together you get sperm production |
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Antagonism
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Antagonistic hormones are hormones with completely opposite functions
- insulin and glucagon Insulin breaks down blood glucose Glucagon elevates blood glucose - They are not released together |
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Suprachiasmatic Nucleus (SCN)
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- some are released in a diurnal pattern
- controls every part of the body that has a diurnal rhythym - it is a collection of cell bodies and sits right above the optic chiasm - advantageous position because the SCN is active based on a 24 hour cycle - controls wide variety of functions- any hormone that is released in a diurnal hormone (melatonin - acts on the brain and has a sedative qualities (produced by the pineal gland)) - Cortisol is controlled by a diurnal rhythm |
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When are hormones released?
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- some hormones are released at all times in low levels
** Some hormones are released only when needed - some are released in regular intervals |
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Pulsatile Release of Hormone
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If we look at the plasma concentration of the hormone with respect to time it regularly increases and decreases
- maximizes target cell sensitivity - if plasma concentration was constant. the cell would desensitize because all the receptors would be used |
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Timing of Hormonal secretion
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- plasma concentrations of gonadal hormones
- pattern that is generated by the regulation of development of particular cells that are required to produce hormone - caused by changing feedback in feedback loops - estrogen and progesterone cycle |
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Control of Hormonal Secretion
- Negative Feedback Regulation |
- Hierarchal levels of control- several endocrine glands release several hormones and the final hormone produced is the hormone that has the ultimate function
- the final hormone provides feedback regulation of the other hormones Endocrine Gland 1 --> Hormone 1 (Tropic) --> Endocrine Gland 2 --> Hormone 2 --> Endocrine Gland 3 --> Hormone 3 --> Target Tissue - the negative feedback is to control hormone number 3- - 2 points of control allow for a more stable production of hormone 3 than if there was 1 point of control |
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Example of negative feedback regulations
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Relationship between the hypothalamus and the anterior lobe of the pituitary gland and several peripheral glands
- the hypothalamus and the pituitary gland are part of the CNS but are endocrine glands - the hypothalamus is located right above the pituitary gland (anterior- true endocrine structure and larger and the posterior lobe is just an extension of the hypothalamus) - hormones that are produced in the hypothalamus are released in the posterior pituitary (Vasopressin/ADH and oxytocin) |
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Hypothalamus and anterior pituitary
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- there are other cells in the hypothalamus that release hypothalamic hormone into a network of capillaries in the base of the hypothalamus
- the network of capillaries carries those hypothalamic hormones directly to the anterior pituitary - they act on endocrine cells in the anterior pituitary to release secondary hormones - those secondary hormones go into circulation and often act on a third endocrine gland in the periphery |
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Hypothalamic Hormone (Endocrine gland 1) --> Anterior Pituitary --> Endocrine Gland
(T3 & T4) |
Thyroid Releasing Hormone --> Thyroid Stimulating Hormone --> Thyroid Gland --> T3 and T4 (Provides feedback to the hypothalamust)
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Hypothalamic Hormone (Endocrine gland 1) --> Anterior Pituitary --> Endocrine Gland
(Cortisol) |
CRH (Cortisol releasing Hormone) --> ACTH --> Adrenal Cortex --> Cortisol (provides negative feedback to hypothalamus and anterior pituitary--> Metabolic actions; stress response
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Negative feedback loop (Prolactin)
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Two hypothalamic hormones regulate prolactin
Prolactin relasing hormone Prolactin inhibiting hormone PRH or PIH --> Prolactin --> Mammary (Exocrine Gland) --> Breast growth and milk secretion - there is a component of breast milk (FIL) feedback inhibition of lactation- provides negative feedback |
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Growth Hormone
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- anterior pituitary hormone
- GHRH- growth hormone releasing hormone --> GH (Anterior pituitary) --> liver (produces insulin like growth factor 1 and 2- Somatomedins) (provides negative feedback |
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Reproductive Hormones
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Hypothalamic hormone -Gonadotropin releasing hormone (GNRH) --> FSH & LH --> Acts on testes and ovaries to produce testosterone, estrogen, progesterone (generally provide negative feedback)
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