Nervous System Lecture Overview

what are the three vital steps within the nervous system?

1. perception

2. integration

3. motor output

central nervous system (CNS)

brain and spinal cord

peripheral nervous system (PNS)

-the sensory and motor divisions that connect the CNS to the rest of the body

-cranial and spinal nerves

visceral sensory division

carries signals from the viscera (heart, lungs, stomach, and urinary bladder)

somatic sensory division

carries signals from receptors in the skin, muscles, bones, and joints

visceral motor division

-carries signals to glands, cardiac muscle, and smooth muscle

-can be sympathetic or parasympathetic

-involuntary

somatic motor division

-carries signals to skeletal muscles

-voluntary

sympathetic division

accelerates respiration, inhibits digestion

parasympathetic division

reduces respiration, stimulates digestion

function of CNS

integration and command center

function of PNS

communication lines between the CNS and the rest of the body

axon

part of the neuron that sends action potentials

dendrite

Branchlike parts of a neuron that are specialized to receive signals

cell body of neuron

contains nucleus and organelles

nissl bodies

Rough endoplasmic reticulum in neuron

multipolar neuron

a nerve cell that has many dendrites and a single axon

bipolar neuron

nerve cell with one axon and one dendrite

unipolar neuron

nerve cell with no dendrites, one axon

anaxonic neuron

many dendrites but no axon

afferent

-sensory; carry information TOWARDS the CNS

efferent

-motor; carry information AWAY from the CNS

ascending tracts

carry information from body up the spinal cord and towards the brain

descending tracts

carry nerve impulses away from the brain

pathways

a bundle of axons that connects 2+ neurons for communication

nerve

A bundle of nerve fibers

plexus

large, interlacing network of nerves

ganglion

A cluster of nerve cell bodies, often of similar function, located in the PNS.

neuroglial cells

supportive cells and make up about half of all neural tissue

astrocytes

brace neurons

form blood-brain barrier

oligodendrocytes

Form myelin sheath in CNS

myelin sheath function

-insulates myelin

-prevents electrical charge from leaking across membrane

-speeds up nerve transmission; allows charge to travel faster down axon

microglia

CNS phagocytes

ependymal cells

line cavities of the brain and spinal cord, circulate cerebrospinal fluid

satellite cells

surround + protect neuron cell bodies in PNS

schwann cells

produce myelin in PNS

diverging circuit

one input, many outputs

converging circuit

many inputs, one output

reverberating circuit

neurons stimulate one another in a sequence

parallel after-discharge circuit

input neuron diverges into multiples chains to eventually reconverges

structural function of spinal cord

-begins at foramen magnum, ends at 1st/2nd lumbar

-provides 2 way conduction path for the braindi

How many pairs of spinal nerves are there?

31

Cauda equina

collection of spinal nerves below the end of the spinal cord

spinal cord functions

conduction, neural integration, locomotion, reflexes

internal gray matter

mostly cell bodies (dorsal horns and anterior horns)

dorsal horns house

interneurons

ventral horns house

motor neurons

exterior white matter

conduction tracts; dorsal, lateral, ventral columns

spinal meninges

dura mater, arachnoid mater, pia mater

dura mater function

-tough outer layer

-protection of brain and spinal cord

arachnoid mater

-middle layer

-subarachnoid space filled with cerebral spinal fluid

pia mater

-thin, delicate, inner layer

-Coccygeal and denticulate ligaments: AKA give spinal cord horizontal support

ascending pathway

carry sensory info to the brain

descending pathway

carry motor info from brain

decussation

where many tracts cross the midline

tract origin ____ to its destination

contralateral

Ipsilateral

on the same side of the body

gracile fasciculus

carries signals from lower body to brain

cuneate fasciculus

ascending tract that carries sensory information from upper extremities to brain

spino____

ascending tract

_____spino

descending tract

ramus

branch of a spinal nerve with both sensory and motor fibers

dorsal rami

serve the skin and muscles of the posterior trunk

ventral rami

form a complex of networks (plexus) for the anterior

phrenic nerve

Carries impulses to the diaphragm from the brain.

sciatic nerve

nerve extending from the base of the spine down the thigh, lower leg, and foot

femoral nerve

innervates quadriceps and skin of anterior thigh and medial surface of leg

Musculocutaneous nerve

coracobrachialis, biceps brachii, brachialis

innervates upper arm

cutaneous innervation

refers to area of skin which is supplied by a specific cutaneous nerve

dermatomes

Skin areas innervated by specific spinal nerves.

reflex arc

sensory receptor, sensory neuron, motor neuron, and effector that are involved in a quick response to a stimulus

what are the 5 components of a reflex arc?

1. receptor

2. sensory neuron

3. integration center

4. motor neuron

5. effector

somatic reflexes

activate skeletal muscle, voluntary

visceral reflexes

Reflex of the autonomic nervous system affecting organs; involuntary

ANS sympathetic division

"Fight or flight"

-causes body to respond to stress

ANS parasympathetic division

"rest and digest response"

-digestion and brings back to homeostasis

ANS autonomic tone

balance between sympathetic and parasympathetic

spinal shock

syndrome of paralysis and absence of reflexes after transection of cord

Neurogenic shock

dangerous drop in blood pressure due to lack of sympathetic nervous system activity

paraplegia

paralysis of both lower limbs due to lesions from T1 to L1

quadriplegia

paralysis of all four limbs due to lesions above C5

hemiplegia

paralysis on one side of body usually due to stroke or brain lesions

cerebrum

Area of the brain responsible for all voluntary activities of the body

diencephalon

Contains thalamus and hypothalamus

midbrain

A small part of the brain above the pons that integrates sensory information and relays it upward.

pons

the part of the brainstem that links the medulla oblongata and the thalamus.

cerebellum

A large structure of the hindbrain that controls fine motor skills, AKA balance and coordination

brain stem

midbrain, pons, medulla oblongata

connects brain and spinal cord

gray matter

Outer part (cortex) of cerebrum and of cerebellum

white matter

myelinated axons, deep in brain

cerebrospinal fluid function (CSF)

buoyancy, protection, chemical stability

what structure makes CSF?

choroid plexus

medulla oblongata nuclei

cardiac center

vasomotor center

respiratory center

pons nuclei

cranial nerves V, VI, VII, VIII

reticular formation function

-Somatic motor control

-Cardiovascular control

-Pain modulation

-Sleep and consciousness

-Habituation

reticular formation clinical impact

Injury to the reticular formation can result in irreversible coma

hypothalamus function

-Hormone secretion

-Autonomic effects

-Thermoregulation

-Food and water intake

-Sleep and circadian rhythms

-Emotional responses

Memory

medullar oblongata function

-Centers for circulatory and respiratory control

-Sensory and motor functions for head and neck

insula function

Taste

visceral sensation

language

cerebellum function

Balance and coordination

longitudinal fissure

separates cerebral hemispheres