Chapter 14: Nervous system DRAFT

CNS

Central nervous system that contains the brain and spinal cord

PNS

Peripheral nervous system

Cranial nerves

Spinal nerves

Ganglia

Sensory input

Sernsory nervous systems detects stimuli and transmits infromation from receptors to the CNS

Somatic sensory

Sensory input from the receptors of the five senses and proporioceptors

Visceral sensory

Sensory input from receptors of internal organs and blood vessels

Somatic motor

Motor output to skeletal muscle

Autonomic motor

Motor output to cardiac muscle, smooth muscle and glands

Motor output

Motor nervous system initates and transmits information from the CNS to effectors

what does the nervous system do

Recieves sensory input, interpret it, and send out commands

• detects envoirment

• process and coordiante information

• Signal proper response

Organization of a nervous system

Sensory receptor sends a sensory input (PNS)

CNS inegrates it

Motor output activates effector cells (PNS)

Important parts of a neuron

Dendrites (sends the nerve impulse to the body)

Cell body

Axon (the output gets sent down here)

Neuolemmocyte (on some, glial cells that speeds up output)

Neufibri node (node of ranvier)

Mylin sheets

Strucutural types of neurons

Uipolar. Short dendrites, long axon with cell body

Bipolar. Dendrites go to cell body which cell to axon

Mutlipolar : long + lots of dendrites that lead to cell body and then send to axon

3 Functional types of neurons

Sensory neurons

Interneurons

Motor neurons

Sensory neurons

Recieves an input

has a cell body of neuron

Sends it into the spinal chord

Afferent transmissions

Interneurons

Works with a signal within the spinal cord

Motor neurons

Push an output to skeletal muscle

efferent transmission

Astrocytes

star-shaped glial cells in the central nervous system that support, nourish, and protect neurons

Anchor neuron to capillary

Blood brain barrier

dorsal caivity isolated from the rest of the body or as best as can be done

Ependymal cells

Make and move cerebrospinal fluid

tells increase SA

Microglial cell

Clean the cerebrospinal fluid, pahocytitic

Oligodendrocyte

Physically support and insulate the axons of neurons in the brain

Satellite cells

Physical barrier between cell body and intrsititial fluid

Neurolemocytes (Schwann cells)

Physically support and insulate the axons of peripheral neurons

CNS glial cells

Astrocyte

Microgial cell

Ependymal cells

Oligodendrocyte

PNS glial cells

Satelite cells

Neurolemmocytes

CNS vs PNS myeliation

Similar but not the same

CNS: Myelination by oligodendrocytes

PNS: Myelination by neurolmmocytes

Both allow salatatory condtion (Node jumping)

Myelination steps

1. Neurolemmocyte starts to wrap around a 1mm portion of an axon

2. Neurolemmocyte cytoplasma and plasma membrane form consectuive layers around axon as wrapping continues

3. The overlapping inner layers of the neurolemmocyte plasma membrane form the myelin sheath

4. Neurolemmocyte cytoplasm and nucleus are pushed to the periphery of the cell to form the neurilemma

Unmyelinated neurons steps

1. Neurolemmocyte starts to envelop mutiple axons

2. The unmyelinated axons are enveloped by the nerolemmocyte, but no myelin shealth wraps around each axon

Action potential phases

1. Depolarization phase: Na+ in

2. Repolarization phase: K+ out

3. Hyperpolarization phase

Action potential values

Resting potential is -65

Peak potential is 40

Hyperpolarization: -80

What changes the membrane potential

Local changes to ion permeability cause changes in membrane potential → change in ion distribution across the plasma membrane

How the action potential works

The action potential proagates itself along the axon

• one way chain reaction; retains strength

Lag time

Frequency of AP reflects strength of stimulus

Speed of nerve impulse

Unmyelinaed: slower, travels continously over full membrane

Myelinated: faster, jumps between nodes of Ranvier

Can increase the speed of transmission of nerve impulse by increasing the diameter of neuron

Neuron regeneration in PNS steps

1. Trauma severs axon

2. Proximal portion severed axon seals off and swells. Distal portion of axon and myelin sheath degenerate ; the nuerilemma survives

3. Neurilemma and endoneurium form a regeneration tube *if cell body and nuerillema reamins, regeneration is possible

4. Axon regenerates and remyelination occurs

5. Innveration to effector is restored

What is a nerve

Bundle of axons in the PNS, surrounded by connective tissue

What is a nerve fasicle

Bundles of axons within nerve

T/F nerve and muscle have similar structure

true

3 types of synaspees based on location

Axosomatic: Axon to cell body

Axodendritic: Axon to dendrite,

Axoaxonic: Axon to axon

2 types of synpases based on function

Eletricial synapse: gap junctions and no delay

Chemical synapse: synaptic delay, involves acetylcholine

Neuronal circit types

Converging: lots of input to one output, like a tree

Divering: less input then output

Reverbrating circuit: feedback loop

Parallel after dischange: parallel lines, lots of input to one output

What does the nervous system do

Coordinates & Integrate nervous activity

How is the neural tubed formed

1. Neural folds and neural groove form from the neural plate

2. Neural folds elevate and apporach one another

3. Neural crest cells “pinch off” from the neural folds and migrate to form other strucutres

4. Neural folds fuse to form the neural tube

What layer forms the neural tube

Medial poriton of ecotoderm rolls up into a tube = CNS