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68 Cards in this Set
- Front
- Back
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Components & function of nervous system |
Components: Brain Spinal cord Nerves Functions: Enables you to control your body + its movements. Ensures body responds appropriately to stimuli at any given time. |
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Neurones |
- Cells that make up nervous system. - Specialised cells, allow body to communicate by carrying information from one part of the body to another. - Bundle together to form nerves. |
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Structure of the NS |
Two components: 1. CNS (brain + spinal cord) 2. PNS-nerves branching into body from CNS (arms + legs)
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PNS |
2 divisions: 1. Somatic: controls voluntary actions (ex. walking) 2. Autonomic: controls involuntary actions (ex. breathing) |
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Autonomic PNS |
2 divisions = compliment each other 1. Sympathetic: fight or flight (prepares body for intense activity) 2. Parasympathetic: rest + digest (relaxes body) |
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Purpose of NS (4 purposes) |
1. Gather information from environmental stimuli 2. Organise information in brain 3. Transmit information from body to brain 4. Transmit an appropriate response from brain to body |
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Stimuli |
- Stimulus: change in environment ---> body react Ex. Light, sound, touch, pressure, pain, chemical change |
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Gather/transmit information |
- Sense organs detect stimuli from internal + external environment - Eyes, ears, tongue, nose, skin - all contain different receptors - Sensory nerves send info from sense organs --> brain. |
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Receptors |
- Group of cells which are sensitive to stimulus. - Change stimulus energy (ex. light) ==> electrical impulses. - Spinal cord + brain |
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Coordinate information |
- Brain collect incoming info from body via spinal cord. - Brain decides on an appropriate response - usually based of memory. |
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Effectors |
- Muscles + glands, respond to signals from the brain - cause body to react (transmit response) Connections Exit to the CNS |
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Motor nerves |
Carry info from brain to effectors |
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Afferent |
connections Arrive to the CNS |
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Neurone |
Cells --> make up nervous system |
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Sensory neurone |
- Carry info from receptors to CNS. - Receives signals from sensory organs + send them via short axons to CNS. |
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Motor neurone |
- Carry info from CNS to effectors (arms + legs). - Conduct motor commands from CNS to muscles. |
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Reflex arc |
- Nerve pathway involved in reflex action - Goes from sensory nerve to spinal cord, immediately out to motor nerve - info does not get sent to brain. - Allows body to react immediately to dangerous stimuli (ex. burning hot stove) |
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Interneurones |
- Interconnect various neurones within the brain/spinal cord. |
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Cell body |
Metabolic control centre, manufacturing + recycling plant. |
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Dendrites |
Receives incoming signals from other neurones - has many within 1 neurone |
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Axon |
Sends outgoing signal to other neurones - only 1 within 1 neurone |
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Axon terminal |
End of neurone, connects w/ other neurones/effectors |
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Neurone features |
Neurones are able to carry information bc they're: - Excitable: detect + respond to stimuli - Conductive: transmit response |
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Electrical signal |
Nerve impulse/action potential - Change in ion balance in nerve cell |
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Chemical signal |
Neurotransmitters |
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Resting Membrane Potential |
RMP: voltage (charge) differences across the cell membrane when a cell is at rest - axon membrane is polarised. - Caused from distribution of charged particles: ions - Positively charges ions: Na+, K+, Mg2+, Ca 2+ - Negatively charged ions: Cl- -Result of unequal ion distribution - electrochemical gradient - Outside positive - Inside negative - Difference in charge = -70 mV |
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RMP: 2 Processes of unequal ion distribution |
1. Active transport: uses protein pump Na+ K+ ATPase - Pumps 3 Na+ out of cell - Pumps 2 K+ into cell - Unequal ion exchange - more + ions leave than come in. 2. Facilitated diffusion: leak ion channels in membrane. - Allow Na+ + K+ ions to move across membrane following gradient (no energy required) - Leaky channels - more K+ channels, therefore more K+ diffuses out of cell. |
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Action Potential |
- Nerve impulses (short-lasting event) - Voltage across membrane rapidly rises + falls, changing electrical potential across membrane. - RMP momentarily reversed. - Inside of membrane becomes more + relative to outside (influx of ions). - Na + K channels are voltage-gated channels - Changes in voltage across membrane cause these channels to open/close. - Na channels open when voltage inside the cell changes to -55 mV. - Neurone that emits action potential is said to fire. - Action potentials occur in neurones (cell-cell communication) muscle cells (contraction) + endocrine cells. |
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Steps of action potential |
1. Depolarisation 2. Repolarisation 3. Hyperpolarisation 4. Refractory period |
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1. |
- Stimulus causes voltage-gated sodium channels in neurone membrane to open. - Na+ ions rush => cell. - Cell's electrical potentials becomes more +. |
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Depolarisation |
- If signal is strong enough, voltage reaches the threshold triggering an action potential. - More Na channels open, allowing influx of Na ions. - Cell depolarises so that charges across membrane are reversed. - Inside of cell, more + charged, outside of cell more - charged. |
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Repolarisation |
- Peak voltage of action potential causes gated Na channels to close + K channels open. - K+ ions move out of membrane. - Na+ ions remain inside membrane. - Repolarisation. |
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Hyperpolarisation |
- Neurone becomes hyperpolarised, more K ions are on outside than Na ions are on inside. - K+ gates finally close - more K+ ions on outside than Na+ ions on inside. - Cell's potential drops slightly lower than resting potential. |
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Refractory period |
- Neurones enters a refractory period. - Na-K pump goes back to work. - Na+ opens moved out of cell. - K+ moved into cell. NO other action potential can be fired at this time, regardless of strength of stimulus. |
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When does the Action potential occur? |
- If stimulus allows enough Na ions entering cell to change membrane potential to a certain threshold level. - If depolarisation is not great enough to reach the threshold, action potential = NO. |
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Myelin Sheath |
- Fatty layering of Schwann cells wraps around the axon. - Insulation to help speed up transmission of impulse. - Gaps between Schwann cells are called nodes of Ranvier - exposed membrane. |
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Saltatory Conduction |
- Action potential 'jumps' from node to node - ion exchange occurs only at nodes of Ranvier, (myelinated nerves). - Used to increase conduction velocity (speed at which nerve impulse travels). |
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Strength of action potential |
- Always the same, regardless to stimulus. - Differences occurs in frequency of action potential being fired. - Stronger stimulus will fire action potential more frequently than a weaker stimulus. |
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Synapse |
The cells does not have direct contact w/ the cell body of the next: the 2 cells are separated by synapse. |
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Presynaptic cell |
Cell carrying signal towards synapse (always neurone). |
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Postsynaptic cell |
Cell carrying signal away from synapse. Either effector cell or neurone. |
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Synaptic cleft |
Gap between axon terminal + another neurone/effector cell. |
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Chemical synapse |
- Converts signals from electrical to chemical back to electrical - allows for different methods of control. - Communication between neurones occurs chemically - neurotransmitters. |
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Neurotransmitters |
- Chemical molecules produced in mitochondria + stored temporarily in vesicles. - Most common: Acetylcholine (ACh) - Involved in CNS (memory, learning + mood) + PNS (activities muscles, contraction). |
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Transmission at a synapse |
1. Action potential arrives to synaptic bulb. 2. Ca2+ channels open in presynaptic membrane - Ca2+ ions rush into the cells. 3. Influx of Ca2+ ions signals synaptic vesicles to move towards the membrane. 4. Vesicles fuse w/ the membrane, releasing the neurotransmitter into the synaptic cleft. 5. Neurotransmitters travels across the synapse to receptors on the postsynaptic cell (synaptic delay). - Neurotransmitter binds, neurone will be excited/inhibited?
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Recycling neurotransmitters |
- Neurotransmitter binds to receptors + causes changes it's immediately released (prevents indefinite impulse firing). - Acetylcholine is broken down in synaptic cleft into acetate + choline. - Re-enters presynaptic cell, converted back into acetylcholine for reuse w/ help from mitochondria. |
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Neuromuscular junction |
- Point where motor neurone makes contact w/ a muscle fibre. - Postsynaptic membrane: muscle end plate. - When neurotransmitters bind to receptors on muscle end plates, muscles fibres contract. |
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Excitatory synapse |
- Neurotransmitter open Na channels on postsynaptic membrane, causing influx of Na ions. - Creates excitatory postsynaptic potential (EPSP). - Enough Na enters, action potential will be generated. - Usually caused from several synapses. |
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Inhibitory synapses |
- Neurotransmitter opens K+ + Cl- channels postsynaptic membrane, causing influx of K + Cl ions - hyperpolarises postsynaptic neurone. - Causes inhibitory postsynaptic potential (IPSP) - Makes it harder for neurone to fire action potential. |
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Function of brain |
Coordination: 1. Receives impulses from receptors 2. Interpret impulses 3. Send out new impulses to effectors |
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Outer brain structure |
1. Cerebrum - Frontal lobe - Temporal lobe - Occipital lobe - Parietal lobe 2. Cerebellum 3. Brainstem |
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Halves of brain |
- Left cerebral hemisphere - controls right side of body. - Right cerebral hemisphere- controls left side of body. |
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Corpus Callosum |
- Connects the two hemispheres - allows signals to be transmitted between each other. - Bundle of nerves. |
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Grey + white matter |
Grey matter: contains cell bodies, dendrites, + axon terminals of neurones ( where all the synapses are) White matter: made of axons connecting different parts of grey matter to each other. |
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Cranial nerves |
- Twelve pairs of cranial nerves (I-XII) emerge from the CNS to form part of the PNS. - Perform sensory + motor functions, mainly in head + neck regions. |
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Cerebral Cortex |
Location: Outermost layer of brain Function: Responsible for thinking + processing information from the five senses. - Made up of tightly packed neurones |
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Frontal Lobe |
Location: Fronta + upper area of the cortex Function: Carries out higher mental processes such as thinking, decision making + planning. - where our personality is formed - if damaged may change our personality. |
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Temporal Lobe |
Location: Bottom middle part of cortex, right behind the temples. Function: Responsible for processing auditory information form the ears. - Allows us to understand + comprehend speech! |
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Occipital lobe |
Location: Bottom, back part of cortex. Function: Responsible for processing visual information from the eyes. - Allows us to make sense of what we are seeing - damage to this lobe may result in visual confusion. |
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Parietal lobe |
Location: Upper, back part of cortex. Function: Processes sensory information that has to do w/ taste, temperature + touch. - If damaged, we would not be able to feel sensations of touch. |
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Cerebellum |
Location: Lower area of the brain, below the cortex. Function: Responsible for balance + coordination of muscles + the body - controls voluntary tasks. - Damage to this area may cause off balance or inability to control muscles. |
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Thalamus |
Location: Above brain stem + below cerebral cortex. Function: Responsible for relaying information from the sensory receptors to proper areas of the brain for processing. - Damaged = sensory info would not be processed. |
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Hypothalamus |
Location: Above brain stem + below the thalamus. Function: Responsible for behaviour such as hunger, thirst + maintenance of body temperature. - Controls the pituitary gland - plays a key role in connecting the endocrine system + nervous system. |
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Pituitary gland |
Location: Below hypothalamus. Function: Produces critical hormones to control other parts of endocrine system. - Damages may cause insufficient/increased release of hormones. |
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Hippocampus |
Location: In each temporal lobe. Function: Responsible for processing of long term memory + emotional responses. - Alzheimer's disease shows damages to this area of the area, as well as amnesia. |
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Amygdala |
Location: The end of hippocampus. Function: Responsible for the response + memory of emotions, => fear. - W/o amygdala, no feel of fear. |
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Pons |
Location: Part of brain stem, sits directly above the medulla. Function: Connects upper + lower parts of the brain, transmits messages between cortex + cerebellum. - Brain wouldn't function w/o pons. |
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Medulla Oblongata |
Location: Lower part of brain stem. Function: Carries out + regulates life sustaining functions (involuntary) eg. breathing, swallowing + heart rate. - Also helps transfer neural messages from the brain to spinal cord. |
