1

Nervous system organization

fig 6-37

2

Brain structure

fig 6-38

3

Brain structure (notes)

Cerebrum structureStructure

lobes: frontal, parietal, occipital, temporal (named for bones)cerebral hemispheres, subcortical nuclei (basal ganglia)

Functionsmotor functions, sensory functionslearning, reasoning, memory

Thalamus (paired)

Hypothalamus (paired)

Cerebellum

Brain stem = midbrain + pons + medulla oblongata

4

Cerebral hemispheres: motor function

fig 10-10

Primary & supplementary motor cortex (frontal lobe)skilled movements, particularly of distal muscles

5

Cerebral hemispheres: motor function

fig 10-11

Primary motor cortexmotor “homunculus”; area related to fine motor control

6

Cerebral hemispheres: basal nuclei

fig 6-39

Basal nucleicoordination of motor activity, control movement & posturedefective in Parkinson’s disease

Corpus callosum:connection between right & left hemispheres

7

Cerebral hemispheres: sensory functionVisual cortex (occipital lobe)Auditory cortex (temporal lobe)Taste cortex (parietal lobe)

fig 7-14

8

Cerebral hemispheres: sensory functionSomatosensory cortex (parietal lobe)

touch, pressure, kinesthesia, temperature, painsensory “homunculus”

fig 7-20

9

Cerebral hemispheres: sensory functionOlfactory cortex (frontal lobe)

only sense not via thalamus, ~1000 odorant receptorsafferent fibers to olfactory cortex & limbic system

fig 7-45

10

Cerebral hemispheres: learning & memory

Declarative memory (language, names, faces, events, facts)Short term:

involves hippocampus & other temporal lobe structuresongoing graded or action potentialssusceptible to shock, trauma, coma, electroconvulsive therapy

Long term:many areas of association cortexinvolves protein synthesis, synapses, post-synaptic receptors

Procedural memory (actions, emotional responses, fears)Short term

various parts of brainLong term

basal nuclei, cerebellum, sensorimotor cortex

11

ThalamusSensory relay (synapses) for all sensory input except olfactory

fig 6-39 (cropped)

12

Hypothalamus

Functions:

regulates anterior pituitary gland (produces releasing factors)

nuclei for posterior gland hormones (antidiuretic hormone & oxytocin)

regulates thirst & hunger

involved in regulation of autonomic system

regulates reproductive system (hormones & autonomics)

circadian rhythms (clock in suprachiasmatic nucleus)

regulates body temperature (integrative center)

important component of limbic system

13

Limbic systemComponents: thalamus, hypothalamus, hippocampus, septal nuclei,

olfactory bulbs, cingulate gyrus

Functions: emotional responses (subjective feeling & behavior), memory

fig 6-40

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Cerebellum

Location: on brain stem, over pons

Input from sensorimotor cortex and vestibular (balance), visual, & musculature

Output to cerebral cortex & brainstem nuclei

Functions:

comparing intended movements with actual outcomes, and making appropriate adjustments; coordinates movements, some procedural memories

Cerebellar disease: intention tremor

15

Brain stem

Components:

mid brain, pons, medulla oblongata

General functions:

ascending & descending pathways

cranial nerve nuclei for III through XII

brainstem nuclei associated with posture, balance & walking

reticular activating system

centers for control of cardiovascular, respiratory, swallowing, vomiting

16

Reticular activating system

Location:

loose network in brain stem, widely distributed input/output

Function:

arousal (positive feedback), wakefulness, awareness, focus

function essential for life

17

Spinal cord

fig 6-41

Gray matter: cell bodies & synapses

White matter: ascending & descending tracts

Ventral root: efferent pathways

Dorsal root: afferent pathways

Dorsal root ganglion: cell bodies of afferent neurons

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Nervous system organization

fig 6-37

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Peripheral nervous system: efferent division

fig 6-43

Somatic: single neuron, innervates skeletal muscle, voluntary control

Autonomic: 2 neuron chain, innervates smooth, cardiac muscle, glands, largely involuntary control

20

Autonomic nervous system: anatomy

fig 6-46 cropped

Parasympathetic: long preganglionic, short post ganglionic, ganglia often in end organ, little divergence, specific action

Sympathetic: short perganglionic, long post ganglionic, much divergenceadrenal medulla: endocrine supplement, acts as a unit

21

Autonomic nervous system: neurotransmitters

fig 6-46 cropped

preganglionic postganglionic

parasympathetic acetyl choline acetyl choline

sympathetic acetyl choline *norepinephrine

adrenal medulla: preganglionic - acetyl cholinepostganglionic (chromaffin cell) - 80% epi, 20% norepi

*someexceptions

22

Autonomic system distribution

fig 6-44

parasympathetic:craniosacral outflowlong preganglionicespecially vagus (X)

sympathetic:thoracolumbar outflowshort preganglionic

23

Autonomic nervous system: actions

General:

parasympathetic (PS): specific actions (rest, digest, rebuild)sympathetic (SY): general action (fight, fright, flight)

Models:

SY: “Og” caveman chased by saber toothed tiger

PS: “Slats Grobnik” lazy, overeating, overdrinking

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Autonomic nervous system: actionsHeart:

PS: rateSY: rate, contractility, cardiac output, blood pressure

Vasculature:

PS: minimal effects

SY: arterioles constrict (especially skin, GI tract, kidneys), veins constrict

Lungs:

PS: bronchioles constrict, secretion

SY: bronchioles dilate, secretion

Gastrointestinal system:

PS: secretions, motility, sphincters relax, blood to salivary glands

SY: secretions, motility, sphincters constrict, blood to salivary glands

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Autonomic nervous system: actionsMetabolism:

PS: anabolic ( insulin), synthesis of fat, glycogen, proteinSY: catabolic ( epinephrine, glucagon, cortisol), lipolysis,

glycogenolysis, gluconeogenesis

Urinary bladder:

PS: sphincter relaxes, bladder wall contracts (micturition),

SY: sphincter constricts, bladder wall relaxes

Sweat:

PS: insignificant innervation (Vander is wrong!)

SY: hands, feet (adrenergic), general (AcCh) – “cold sweat”

Reproductive system:

PS: erection (penis, clitoris) – NO is neurotransmitter, not AcCh

SY: ejaculation (male), orgasm (female)

26

Adrenergic receptors

Norepinephrine (NE) and epinephrine (E) bind to “adrenergic” receptors

Examples: 1, 2, 1, 2, 3

NE & E bind to all types, although NE prefers ’s & E prefers ’s

1 receptors: cause smooth muscle contraction (e.g. arterioles, veins)

have IP3, DAG, Ca++ as second messengers

1 receptors: are in (1) heart and mediate cardiac responses to SNS

have cAMP as second messenger

2 receptors: cause relaxation of smooth muscle (e.g. (2) lung bronchioles)

have cAMP as second messenger

Smooth muscle response depends on receptor profile