April 3rd 2014 What were neurons again? The Neuron

https://www.youtube.com/watch? v=W4N-7AlzK7s&list=UUX6b17PVsYBQ0ip5 gyeme-Q The Neuron

dendrites: short branches that conduct impulse towards cell body

cell body/soma: contains the nucleus and other organelles

: long projection that conduct impulse away from cell body

axoplasm: electrically-conductive cytoplasm within the axon that transmits impulses

axomembrane: plasma membrane of neurons that is responsible for maintaining the axon's membrane potential The Neuron

Neuron are packed together into nerves

nerves can contain a mixture of neurons (sensory & motor) that send info in both directions to different places

not all neurons form nerves

ganglion: neuron cell body cluster in the PNS The Neuron - Myelin Sheath

Myelin Sheath: fatty layer composed of Schwann Cells that wrap around the axon The Neuron - Myelin Sheath

Functions:

a) insulates the neurons from each other as they are tightly packed together within a nerve

b) accelerates impulse transmission Myelin Sheath Degeneration Myelin Sheath Degeneration

Multiple Sclerosis - autoimmune attack on myelin sheath

https://www.youtube.com/watch? v=VIoDr8ugbqI The Neuron - Axon

Node of Ranvier: points between Schwann Cells

Saltatory transmission: the "jumping" transmission of impulses from one node of Ranvier to the next The Neuron The Neuron 3 Types of Neurons

Sensory Neurons

Interneurons

Motor Neurons Connecting PNS & CNS Reflex Arc

1. Sensory Receptor

2. Sensory (afferent) neuron

3.

4. Motor (efferent) neuron

5. Effector (muscle/ gland) Reflex Arc Reflex Arc

http://youtu.be/wLrhYzdbbpE 1. Receptor

Detects stimuli - if stimuli are strong enough past a certain threshold, an impulse is initiated in the

stretch receptors in blood vessels

pain receptors in skin

photoreceptors in eyes

chemoreceptors in heart & Some people are born without pain receptors = dangerous 2. Sensory Neuron

contain sensory receptors that detect stimuli

long myelinated dendrites & short axon

cell body is outside of the in the ganglion

function: carry sensory impulses toward the CNS 3. Interneuron

entirely in the spinal cord/CNS

short dendrites & axon

function: connect the sensory and motor neurons 4.

short dendrites & long myelinated axon

dendrites are in the spinal cord, axon is outside of spinal cord

axon endings attached to effector (muscles)

function: carry impulses from the CNS to effector (muscle/ gland) 5. Effector

Muscles or glands

When stimulated by the motor neuron:

muscles will contract

glands will release a hormone Inherent vs. Conditioned Reflexes