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87 Cards in this Set
- Front
- Back
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Major Brain Divisions
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Cerebrum
Diencephalon Cerebellum Brain Stem |
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Cerebrum
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Higher Thought Processes
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Diencephalon
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Corntrols vital functions and regulates other regions of the brain
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Cerebellum
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Produces smooth, coordinated skeletal muscle activity
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Brain Stem
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Relay station for messages to and from brain
Also controls reflexes (visual, breathing, heartbeat, vomiting) |
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Protection of the brain
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Cranium (skull)
Meninges (3 layers of tissue) Cerebrospinal (In the ventricles) Blood brain barrier (selective permeability of neurons & harmful substances) |
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Meninges
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Connective tissue membranes that surround the brain and spinal cord
Dura - two fibrous connective tissue layers Arachnoid - clear middle layer Pia - inside layer |
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Cerebrospinal Fluid
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Circulates in ventricles and subarachnoid spaces.
Cushions the brain reduces weight by 97% Nourishes the brain and reduces waste products produced by choroid plexi in the ventricles |
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Ventricles
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enlarged chambers in the brain and the hollow central canal of the spinal cord.
contain csf continuous with one another and the central canal of the spinal cord lined with ependymal cells (neuroglia) that produce the CSF |
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Choroid Plexuses
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Clusters of capillaries that hang from the roof of each ventricle
Produce CSF Remove wastes from CSF Replaced every 8 hours and circulate slowly through the cns Produce 500 ml/day - 1/2 liter. |
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Blood Brain Barrier
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Neural tissue is separated from the general circulation by the blood brain barrier no other tissue is so dependent on a constant internal environment
Selective, not absolute. Allows nutrients (glucose) to pass freely Endothelium of capillary walls in the brain have continuous tight junctions of electrical resistance providing an effective barrier against molecules. |
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Surface anatomy of brain
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Gyri (ridges)
Sulci - (shallow grooves) Fissures -(deep grooves) |
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Cerebrum
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Most important/most complex
83% of brain mass 2 halves - separated by longitudinal fissure |
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Crainial hemispheric region Composition
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Cortex - Gray matter
White matter - Mostly mylenated basal nuclei - islands of gray |
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Lateralization of hemisphere function
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Exhibits contralateral control
(rt. brain/left motor) Lateralization each has abilities not shared with the other |
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Functional areas of cerebral cortex
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Motor - voluntary movement
Sensory - Conscious awareness of sensation Association - interpret sensory data or coordinate motor response |
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Primary Motor Cortex
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Conscious control of voluntary momement.
anterior to central sulcus |
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Broca's Area
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Speech - Anterior and inferior to the pre-motor area - usually only in left hemisphere
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Primary Somatosensory cortex
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Located behind the central sulcus
receives info from skin and proprioceptors in skeletal muscles, tendons and joints. spatial discrimination |
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Visual Areas
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Largest of sensory cortex areas
Receives visual data from the retinas. Interprets visual stimuli (e.g., color, form, and movement) based on past experience |
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Multimodal Association areas
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“give meaning” to the sensory data, based on memory and experience.
ie. is it pleasurable or harmful, urgent or routine, etc.? Then the association area develops a “plan of action” for dealing with the sensory data – this is the “cognitive higher thinking” activity of the brain Then the decision of what to do is sent to the pre-motor cortex and then onto the motor cortex, then through cerebellum for final coordination, organization |
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Anterior association area
Prefrontal cortex |
involved with intellect - complex learning abilities
**Most complex cortical region Involved with intellect *, complex learning abilities** (cognition) recall, and personality Contains working memory – necessary for the production of abstract ideas, judgment, reasoning, persistence, and planning |
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Limbic System
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Emotional Response - memory center
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White matter tracts
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Tracts of white matter are named by the direction that they travel
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Projection fibers
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Projection fibers - connect the hemispheres to lower brain or the spinal cord.
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Association fibers
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Connect different parts of the same hemisphere from one lobe to another
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Commisures
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Connect corresponding gray matter of the two hemispheres enabling them to act as one
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Cerebellum
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Gray and white matter - about 11% of brain mass.
Acts like an orchestral conductor to coordinate instruction from higher cortical areas to ensure smooth movement Operates on a subconscious level...no awareness of it. |
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cerebral processing
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motor areas notify the cerebellum of intent to move a musclMeanwhile the cerebellum is receiving info from proprioceptors in body
The cerebellar cortex calculates the best way to coordinate Then, the cerebellum sends it’s plan , or “blueprint’ for movement back to the cerebral motor cortex |
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Diencephalon
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Thalamus and Hypothalamus
Controls autonomous Nervous system |
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Thalamus
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The primary relay station for information heading up into the cerebral cortex. Afferent (sensory) impulses from all senses synapse with at least one of thethalamic nuclei.
Information is sorted and grouped if similar, then forwarded to appropriate area in cortex Thalamus plays a key role in mediating sensation, Motor activities, cortical arousal, learning and memory. It is truly the gateway to the cerebral cortex. |
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Hypothalamus
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Parasympathetic
It’s the main visceral control center of the body, and is essential for maintaining homeostasis. Some of its functions include Initiates physical responses to emotions…chills, tension, etc. Regulate body temperature. Regulate food intake – hunger vs. satiety Regulate water balance and thirst Regulate sleep-wake cycles Control endocrine system function |
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Brain Stem
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Three regions – midbrain, pons, and medulla oblongata – collectively accounts for only about 2.5% of brain mass
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functions of brain stem
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Midbrain – involved in pain suppression, fear perception and fight-or-flight responses
Pons – composed mostly of projection fibers – connecting cortical areas with the spinal cord, and connects to both sides of the cerebellum Medulla – plays a crucial role as an autonomic control center – involved in maintaining body homeostasis |
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Spinal Cord
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Begins where medulla oblongata transitions into the cord as it exits foramen magnum of occipital bone
Cord is wider at cervical & lumbar areas due to more neurons needed to control the numerous muscles of upper and lower extremities |
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Conus medullaris
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is the bottom (terminal) end of the spinal cord proper
Nerves supplying the lower limb continue down the vertebral canal to form the cauda equina (horse’s tail) |
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Filum terminale
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fibrous extension of the pia mater; anchors the spinal cord to the coccyx
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Spinal nerves
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31 pairs attach to the cord by paired roots
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Gray Matter: Organization
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Dorsal half – sensory roots and ganglia
Ventral half – motor roots – cord is wider at cervical & lumbar areas due to more neurons needed to control the numerous muscles of upper and lower extremities Dorsal and ventral roots fuse laterally to form spinal nerves |
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White Matter in the Spinal Cord
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Consists of myelinated and unmyelinated fibers that allow communication between different parts of the spinal cord & between the cord and the brain
Three directions – ascending, descending, and transversely Divided into columns on each side |
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ascending
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Sensory
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Descending
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Motor
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Ascending (Sensory) Pathways
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First-order neurons conduct impulses from sensory receptors to the cord
Second-order neurons in the cord conduct impulses to the thalamus or cerebellum Third order neurons take the message from the thalamus to the sensory cortex Names usually begin with Spino- eg: spinothalamic tract , spinocerebellar tract, etc. |
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Peripheral Nervous System (PNS)
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Consists of all neural structures outside the brain and spinal cord
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Sensory Receptors and Sensation
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Sensory receptors are specialized structures designed to respond to changes in their environment - stimuli
Activation of a sensory receptor results from an adequate stimulus that causes a nerve impulse to be sent along an afferent PNS fiber to the CNS |
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Mechanoreceptors
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respond to mechanical force such as: touch, pressure, vibration, and stretch
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Thermoreceptors
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respond to changes in temperature
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Photoreceptors
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respond to light energy (retina)
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Chemoreceptors
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Chemoreceptors – respond to chemicals in solution (smell, taste, changes in blood chemistry or interstitial chemistry)
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Nociceptors
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respond to potentially damaging pain-causing stimuli (searing heat, extreme cold, excessive pressure)
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Extroreceptors
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Respond to stimuli arising outside the body: touch, pain, temperature, light,sound etc.
Located in the skin and special senses – sight, hearing, taste, smell, etc. |
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introreceptors
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(also called visceroreceptors)
Respond to stimuli arising within the body - chemoreceptors, pressure receptors, thermoreceptors, osmoreceptors (thirst) |
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Proprioreceptors
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Respond to the degree of stretch of their surrounding tissue
Found in skeletal muscles, tendons, joints, ligaments, and connective tissue coverings of bones and muscles Constantly “advise” the brain of one’s body position and movements |
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Receptors Classified by Receptor Structure
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Two basic types: Simple and Complex
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Simple
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overwhelming majority of sensory receptors, found throughout body – handle general sensory information
Can be Unencapsulated or Encapsulated |
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Complex
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found in Special Senses - vision, smell, hearing, taste, and equilibrium
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Processing at the Receptor Lever
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The stimulus must have specificity for the type of receptor
i.e. touch vs light vs temperature Stimulus energy must be sufficient to exceed the receptor's threshold and cause an action potential in the neuron Stimulus must be applied within a receptor’s receptive field - the smaller the field, the better the brain can localize the stimulus site |
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Processing at the Perceptual Level
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The ability to identify and appreciate sensations
depends on the location of the sensor and the target area of the brain. The thalamus projects fibers to the appropriate somatosensory cortex or sensory association areas for interpretation Perception of the sensory stimulus includes: Magnitude estimation - intensity of stimulus Spatial discrimination – 2 pt test Feature abstraction-specific texture or shape (velvet versus fur or cotton) Pattern recognition – (e.g., melody, familiar or unfamiliar face) |
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Nerve
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primary organ of the PNS consisting of peripheral axons enclosed by connective tissue
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Endoneurium
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loose connective tissue surrounding one axon
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Perineurium
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coarse connective tissue that bundles fibers into fascicles
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Epineurium
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tough fibrous sheath around a nerve
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Peripheral Nerves
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Nerves can carry messages that are sensory (afferent), motor (efferent), or both
Mixed nerves (most common) – carry sensory and motor impulses Purely sensory or motor nerves are rare Nerves are classified by the area served Somatic afferent and somatic efferent Visceral afferent and visceral efferent |
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Cranial Nerves
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The cranial nerves arise directly from the brain – hence the name
There are twelve pairs of cranial nerves They have sensory, motor, or mixed functions Each nerve is identified by a number (I through XII) and a name The first two originate from the forebrain – Olfactory I, and Optic II, the rest arise from brainstem All serve head and neck areas – except the Vagus (X) nerves which reach to the abdomen |
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Spinal Nerves
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Thirty-one pairs of mixed (sensory & motor) nerves – each contains 1000s of fibers - arise from the spinal cord and supply all parts of the body except the head
They are named according to their point of issue Each has a dorsal (sensory) and a ventral (motor) root The roots join just distal to the dorsal root ganglion and form the spinal nerves |
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Nerve Plexuses
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Interlacing nerve networks are called plexuses
Plexuses are found in the cervical, brachial, lumbar, and sacral regions Each resulting branch of a plexus contains fibers from several spinal nerves All spinal nerves except T2-T12 are involved in plexi |
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Cervical
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C1-C8
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Thoracic
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T1-T8
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Lumbar
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L1-L5
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Sacral
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S1-S5
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Coccogyeal
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CO 1
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Nerve Plexuses
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Interlacing nerve networks are called plexuses
Plexuses are found in the cervical, brachial, lumbar, and sacral regions Each resulting branch of a plexus contains fibers from several spinal nerves All spinal nerves except T2-T12 are involved in plexi |
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Reflexes
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Reflexes may:
Be inborn (intrinsic) - a rapid, predictable motor response to a stimulus or learned (acquired) Can involve higher brain centers as well, which can modify the reflex Example: You would drop a pot of boiling water if it splashed on you. (inborn) What if a child was by your side? (acquired) Reflexes follow very specific neural pathways called a Reflex Arc Reflexes are classified functionally as somatic reflexes if they activate skeletal muscles or as autonomic reflexes if they activate visceral effectors (glands or smooth or cardiac muscles) |
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Stretch and Tendon Reflexes
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The brain “sets” a muscle length and the stretch reflex ensures it stays at that length
Ex: Patellar (knee-jerk) reflex Tapping the patellar tendon stretches the quadriceps The change in length is sensed by muscle spindles: specific types of proprioreceptors that detect muscle length Spinal reflex is initiated The quadriceps contract and the antagonistic hamstrings relax (reciprocal inhibition) Helps to maintain standing and walking posture (prevent knee buckling) |
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Golgi Tendon Organs
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Special receptors that sense muscle tension
When tension is excessive, the Golgi tendon organs begin a reflex that causes the primary muscle to relax. Causes “weightlifting failure” This is the opposite of the stretch reflex Note: the muscle spindle stimulates a muscle to contract the golgi tendon organ inhibits muscle contraction |
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The ANS has two divisions
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sympathetic/parasympathetic
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Parasympathetic
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handles routine maintenance issues - homeostatic mechanisms it conserves energy - “rest and digest”
three Ds – digestion, defecation, diuresis |
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Sympathetic
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mobilizes the body during activity
three Es – exercise, excitement, emergency “fight or flight” responses also handles normal activity increases – sports, etc. constricts visceral blood vessels to get more blood to skeletal muscles dilates the bronchioles to increase ventilation causes liver to release more glucose for cellular energy |
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Comparison of the Autonomic Nervous System to the Somatic Nervous System
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The effectors of the SNS are skeletal muscles
The effectors of the ANS are: cardiac muscle smooth muscle blood vessels, bronchial tubes, GI tract, urinary bladder, eye, hair follicles and sphincters glands sweat, lacrimal, salivary, digestive, endocrine, etc. |
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Comparison of the ANS to the Somatic Nervous System
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Axons of somatic motor neurons extend from the CNS to the effector muscle - one neuron
Axons of the ANS are a two-neuron chain The preganglionic (first) neuron The postganglionic (second) neuron extends to an effector organ, gland |
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Comparison of the ANS to the Somatic Nervous System
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All somatic motor neurons release acetylcholine (ACh)
************ Acetylcholine (ACh) and norepinephrine (NE) are the two major neurotransmitters of the ANS In the ANS: All preganglionic fibers release Ach – excitatory Sympathetic postganglionic fibers release norepinephrine and epinephrin (adrenalin) at synapse with effectors Parasympathetic postganglionic fibers release acetylcholine at synapse with effectors |
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Interactions of the Autonomic Divisions
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Most organs have both sympathetic and parasympathetic fibers
For the most part, the parasympathetic and sympathetic divisions work in direct antagonism to each other ex: after eating, it’s a good idea to relax for a bit – let digestion activities proceed without sympathetic interference ex: during vigorous exercise, visceral vessels constrict to direct blood flow to muscles, lungs and heart In normally functioning homeostasis, the result is a dynamic antagonism that precisely controls visceral activity |
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Anatomy of ANS
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The anatomy of the parasympathetic and sympathetic divisions differs
in three significant ways |
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Sites of origin of fibers:
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Parasympathetic fibers are craniosacral (90% in Vagus nerve)
Sympathetic fibers are thoracolumbar |
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Relative lengths of fibers
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Parasympathetic – long preganglionic, short postganglionic
Sympathetic – short preganglioic, long postganglionic |
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Location of ganglia
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Parasympathetic – most are in the visceral effectors
Sympathetic - close to spinal cord in sympathetic chain |
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Parasympathetic Division
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Cranial Outflow is through the Oculomotor (CNIII), Facial (CNVII),
Glossopharyngeal (CNIX) and Vagus (CNX) nerves (90%) - Vagus nerve serves virtually every organ in thoracic and abdominal cavities Sacral Outflow is through spinal levels S2-S4 – controls distal half of large intestine, urinary bladder, ureters, and reproductive organs |
