Unit 6 Nervous system

What are the functions of the Nervous system

• receives & processes sensory info

• coordinated actions of skeletal muscles

• controls all internal organ system

• thinking & memory

What is part of the CNS

Brain & spinal cord

What is part of the PNS (peripheral NS)

• autonomic nervous system

• peripheral nerves

• enteric nervous system

Order information processing

Nervous (neural) tissue consists of two cell types

Neurons and neuroglia (glial cells)

What are neurons

nerve cells responsible for transferring and processing info in nervous system

What are neuroglia (glial cells)

supporting cells and protect neurons

What do neurons do

for rapid communication, receive and transmit info with electrochemical impulses called action potentials

Neuron characteristics

• excitability

• conductivity

• secretion

• longevity

• amitotic

What is excitability (neuron characterstic)

ability to respond to stimuli

What is conductivity

transmit signals between places

What is secretion

neurotransmitter release signaling molecules to communicate to other cells

What is longevity (neuron characteristics)

keep them until we die

What is amitotic

few neurons divide post birth

Neuron structure- what is it pointing at and what does it do?

• soma

• cell body or nucleus

• info processing can happen

Neuron structure- what part of the neuron is it pointing at & what does it do?

• dendrites

• neuronal processes

• inputs

• how neurons bring in info

Neuronal structure - What is this & what does it do

• Axon

• neuronal process

• outputs

• where action potentials starts

What part of the axon is this?

• axon hillock

• junction between soma and axon

• origin site of action potentials

What is a myelin sheath?

transfers info (signal) from cell body down to axon terminal

Neuronal shapes: typically single axon & multiple dendrites

• most common type in CNS

  • in brain & spinal cord

multipolar

Neuronal shapes: cell body is between dendrite & axon

• axons are not myelinated

• typically in PNS sensory branches (afferent side)

Bipolar

Neuronal shapes: cell body is off to one side of axon

• sensory neuron

• input & output arm

unipolar or pseudo unipolar

What are the 3 major functional groups of neurons

sensory neurons, motor neurons, interneurons

Which functional group of neurons:

• axons are afferent fibers

• sends info from PNS to CNS

• there are: somatic sensory neurons & visceral sensory neurons

Sensory or afferent neurons

Which function group of neurons:

• axons are efferent fibers\

• sends info from CNS to PNS

• consists of two divisions

  • somatic motor neurons & visceral motor neurons

motor or efferent neurons

Which functional group of neurons:

• located in CNS

• situated between motor & sensory neurons

• analyze sensory input & coordinate motor outputs

• “processes” information

• can be excitatory or inhibitory

• most common neuron type

interneurons

Which sensory (afferent) neuron:

• senses stimuli on the skin & within skeletal muscles

somatic sensory neurons

Which sensory (afferent) neurons):

• senses stimuli inside body (organs, tubes, etc)

Visceral sensory neurons

For motor (efferent) neurons:

• controls skeletal muscles that move body in voluntary movements

somatic motor neurons

For motor (efferent) neurons:

• controls smooth, cardiac, & skeletal muscles for involuntary contractions

visceral motor neurons

For interneurons what does it mean:

• messages cause other neurons or cells to be more active

excitatory

For interneurons what does it mean:

• messages cause other neurons or cells to be less active

inhibitory

Neuroglia

• what cell supports neurons & their activities

  • insulate myelin on the axon

  • maintain extracellular environment around neurons → keeps neurons healthy

Glial cells (neuroglia)

Neuroglia

• help dilate/constrict blood vessels in response to neural activity

• transport blood to neurons

• found near neurons & blood vessels (mainly in CNS)

• help transfer material from blood to nervous system

• blood-drain-barrier

• many in the brain

Astrocytes

What is the blood-drain-barrier?

established by astrocytes, protection for neurons from getting exposed to toxins

• surround some of PNS neurons

• version of astrocytes that are found in the PNS

• maintain extracellular environment

• act as a bridge between the NS & circulatory system

Satellite cells

• found in lining of cavities of brain & spinal cord

• AKA ventricles → flow fluid (CSF0 around so neurons have CSF

• make cerebrospinal fluid (only in CNS)

Ependymal cells

• aren’t actually neural tissue

  • born in immune system

  • destroy foreign particles

Microglia

• many layers of glial cell plasma membrane wrapped around axon

• insulation → makes conduction of impulses faster

Myelin sheaths

• saltatory conduction - action potentials jump from node to node

• gaps between myelin

• action potentials jump from nodes

nodes of ranvier

Neuronal Communication

• uneven distribution of + & - ions across plasma membrane

• when there is an action potential there is a rapid change

membrane potential

slower impulse speed

unmyelinated

faster impulse speed

myelinated

faster conduction speed

larger axon diameter

slower conduction speed

smaller axon diameter

Junction between a neuron & another cell

synapse

What are the 2 major types of synapses

chemical synapse and electrical synapse

Type of synapse

• communicating cells do not touch

• sending cells releases chemical messenger (neurotransmitter) which is received by receiving cell

chemical synapse

Type of synapse

• communicating cells physically connected by gap junction

electrical synapse

What is the sending neuron & what is the

Part of the CNS

• brings in & processes information

• can function independently of the brain

spinal cord

Part of the CNS

• integrates & processes info

• works with ____

brain

Where is the brain & cavity located (cavities)

posterior cavities

• thin specialized membranes that provide protection, physical stability, and shock absorption

• covers CNS

• made of 3 layers

meninges

Layer of meninges

• tough, fibrous outermost layer

• stabilizes spinal cord

• within the vertebral canal

• cranial & sacral attachments stabilize

• longitudinal axis of spinal cord

• epidural space: space between dura mater & lining of vertebral bones

dura mater

Layer of meninges

• middle layer

• separated by subarachnoid space

• ____ trabeculae extend from arachnoid to outer layer of pia mater

  • spider web-like matrix of trabeculae

  • cerebrospinal fluid flows within spaces between trabeculae

arachnoid mater

Layer of meninges

• innermost layer (adjacent to spinal tissue or brain tissue)

• blood vessels are found here

• protection in case foreign debris get past

pia mater

• consists of neuronal stomata (cell bodies), dendrites, unmyelinated axons

• glial cells

• found in superficial part of brain

gray matter

• neuronal axon (myelinated)

• found deep in brain

• superficial in spinal cord

• where info is sent from one place to another → goes through spaces

white matter

How many pairs of spinal nerves are there?

31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal

What is the difference between the dorsal root and ventral root

dorsal root carries sensory or afferent information to the CNS; ventral root carries motor or efferent commands away from the CNS

What is the Cauda Equina

bundle of spinal nerve roots extending below the end of the spinal cord, look like a horse’s tail

Primary function of the thalamus

acts as a relay station, processing and directing sensory information to the appropriate areas of the cerebral cortex

Whare the 3 regions of the Brainstem

midbrain, pons, and medulla oblongata

function of cerebellum

integrates sensory information to coordinate motor movements, balance and motor learning

Which lobe is responsible for voluntary motor control & personality

frontal lobe

Where is the somatosensory cortex located and what is it responsible for

parietal lobe, responsible for touch, temperature, and pain