Nervous SystemCompare the functions of the CNS & PNS

Identify the principle parts of the nervous system

Describe the cells that make up the nervous system

Describe what starts and stops a nerve impulse (action potential)

The role of neurotransmitters Compare the functions of the CNS & PNS Identify the principle parts of the brain

Objectives

Components of the Nervous System - Somatic

CNS = spinal cord & brain PNS = nerves carry (tissue) impulses to and

from brain Motor Output side of chart has 2 divisions:

somatic and autonomic Focus Somatic 1st then Autonomic

Requires only one neuron system: CNS to cell 12 pairs cranial nerves

◦ From brain’s underside/brain stem◦ Brain to muscles, glands, head, neck, thorax,

abdomen 31 pairs spinal nerves

◦ Originate from spinal cord◦ Dorsal root ganglia– sensory incoming AP from

tissues to cord◦ Ventral root ganglia– motor outgoing AP away from

cord to body Connects CNS to body parts

Somatic division/Motor/PNS

Spinal Reflexes – require no conscious thought – processes @ spinal cord only

E.g. flexor reflex – withdrawal of foot from something sharp

Knee-jerk reflex (check up) – tap below patella causes contraction of thigh and upward movement of foot and leg

Stretch (quadriceps) reflex – posture maintenance – stand and move w/out having to think about it

Reflexes

Components of the Nervous System-autonomic

Sympathetic – stress / high activity Parasympathetic – resting, homeostasis 2 neuron system to transmit impulses to

target cells 1st neuron - preganglionic in CNS 2nd neuron – postganglionic outside CNS &

extending to the far reaches of the body (glands/organs)

Sympathetic & Parasympathetic oppose each other – work antagonistically for homeostasis

Autonomic Division

Neurotransmitters◦ Sympathetic – norepinephrine (adrenalin) - stress◦ Parasympathetic – acetylcholine - relax

Sympathetic vs. Parasympathetic

Somatic and Autonomic Divisions of the PNS

Components of the Nervous System

Central location & action

Integrating & processing of information

Info in CNS Complex Output

Brain & Spinal Cord

“Billions of action potentials travelling in millions of neurons all come together as a conscious thought”

Normal thoughts Dark thoughts

Could this be what stress looks like?

Comic thoughts…

Reflexes and the reflex arc – terms 142-143 Learning Target #5 (Nervous System) p 135:

Describe the structure of a reflex arc and the function of a reflex

Assignment 3.23

Bone, meninges & blood-brain barrier Bone: skull & hollow vertebrae Meninges: CNS enclosed by 3 membranous

layers◦ Out In◦ Dura matter – arachnoid matter – pia matter

Protection of CNS

Figure 11.14ab

CNS is bathed in cerebrospinal fluid Fills the space between the arachnoid

matter & pia matter

Functions as a liquid shock absorber

Isolates the CNS from infection (meningitis: bacterial or viral infection of meninges can spread to CNS)

CNF (cerebrospinal fluid)

CSF is like the interstitial fluid that bathes all cells but it does not exchange substances as freely with blood

Capillaries in this area are “tight” = not leaky & substances must pass through the actual capillary cells (vs. slipping between narrow slits of adjacent capillary cells) to get from blood to the brain

More about CSF

Lipid soluble substances pass easily (O & CO2)

Glucose requires active transport Larger molecules: proteins, viruses,

bacteria kept out What can pass through BBB?

◦ Alcohol◦ Caffeine◦ Nicotine◦ Cocaine◦ Anesthetics

Blood-brain barrier

Information super highway for APs between the brain and the body

Recall – spinal reflexes don’t involve brain and therefore are considered “unconscious”

Size – about the diameter of your thumb

Location – runs from the base of your skull to the area of the 2nd lumbar vertebra ~ 17 inches

Spinal cord

Figure 11.13b

Figure 11.10

Outer portions of the cord consist of bundles of axons = nerve

tracts that are mylenated = white matter – ascending sensory nerves & descending motor nerves

Inner portions consist of cell bodies, dendrites, neuroglial cells

that are unmylenated = gray matter – here sensory & motor neurons synapse & transmit to the brain…

Inside the spine

Figure 11.14