Bio 30 Nervous System

What is the nervous system?

elaborate system that:

receives sensory input
processes, integrates and stores info
triggers response

Homeostasis

The tendency of the body to maintain stable internal conditions at an equilibrium

Ex. body temp, blood pH, blood pressure

Neuron

functional unit of the nervous system

What are the 2 subdivisions of the nervous system?

CNS, PNS

CNS (Central nervous sytem)

composed of brain and spinal cord

PNS (peripheral nervous system)

composed of numerous nerves that extend from spinal cord

Somatic Nerves

Voluntary
bring sensory info to CNS about external environment

Autonomic nerves

involuntary
bring sensory info to CNS about internal environment

What is the autonomatic nervous system divided into?

Sympathetic: responds to stresses

Parasympathetic: regular functions like digestion, opposite of Symp bc/ bring body back to normal

Summarize the Nervous System

What 3 layer protective membrane surrounds the Brain

meninges

order from farthest to closest of meninges

dura mater, arachnoid mater, pia mater

cerebrospinal fluid

circulates between innermost and middle meninges

acts as shock absorber

can be extracted via lumbar puncture

Function of the brain

control centre

receives, processes, integrates, and stores info

higher cognitive functions

regulates involuntary and voluntary functions

3 main sections of the brain

forebrain, midbrain, hindbrain

parts of the forebrain

Cerebrum, cerebral cortex, olfactory bulbs, thalamus, hypothalamus, pituitary

4 lobes of cerebrum and function

frontal: judgment behaviour and impulse control, decision making, complex motor movements

temporal: auditory processing

parietal: sensory processing of touch, taste

occipital: visual processing

cerebral cortex

surface of cerebrum

sulci

grooves of cerebral cortex

geri

bumps of cerebral cortex

motor homunculus

diagrammatic representation of body part size as proportional to area of cortex controlling it

Right hemisphere

visual patterns and spatial awareness

Left Hemisphere

verbal skills and analytical thought

Corpus Callosum

bundle of nerves that serve as connection between 2 hemispheres

thalamus

conducts sensory info to appropriate lobe

hypothalamus

plays role in regulating internal equilibrium

olfactory lobes

receives and interpret info about smell

Midbrain

Tectum

Tegmentum

Relays sensory signals to appropriate lobes

Hindbrain

includes cerebellum, pons, and medulla oblongata

cerebellum

regulates balance, posture and coordination

limb movements, balance, and muscle tone

pons

bridge for cerebellum and medulla oblongata

medulla oblongata

connected to spinal cord

mian region for autonomic nerve control

controls involuntary vital functions required for homeostasis

Spinal cord

conducts sensory nerve messages to brain and carries motor messages to rest of body

foramen magnum

hole at base of skull where spinal cord meets brain

vertebrae

bone that protects spinal cord

where is grey and white matter in spinal cord and brain

spinal cord: grey surrounded by white

brain: white surrounded by grey

2 types of cells in nervous system

glial cells: non - conductive; supportive cells

Neurons: conductive transmit impulses and secrete neurotransmitters; carry out nervous response

parts of the neuron

dendrites, cell bodies, axons, axon terminal

Dendrites

branches extend from cell body

receive info from env or other neuron

cell body

part of neuron that looks like typical cell; contains neurons and other important organelles

axon

long part of neuron

electrical impulses travel down axon

axon terminal

transmit info to either effector organ or another neuron

nerves

bundle of axons surrounded by connective tissue

ganglia

cluster of neuron cell-bodies

3 types of neurons

sensory - afferent

motor - efferent

interneuron - association neurons

Sensory neurons

relay info about internal/external environment received by sensory receptors to CNS

Interneurons

link between sensory and motor neuron; only in CNS

Motor Neurons

carries nervous impulse from nervous system to effector

effector

cells/tissues/organs that produce a physiological response when stimulated

SAME - DAVE

(sensory - afferent, motor - efferent; dorsal - afferent, ventral - efferent)

Reflex

involuntary response to a stimulus

Reflex arc

neural circuit through spinal cord that bypasses Bain to produce reflexive response to stimuli

nerve pathway of reflex arc

stimulus —> sensory neuron —> interneuron —> motor neuron —> effector

Examples of reflexive responses

achilles tendon reflex, patellar reflex, pupillary reflex

electrochemical

conduction of charges via movement of charged chemical substances (ions)

nerve impulses are electrochemical messages

membrane potential

difference of charge across a cell membrane (exterior and interior axon)

resting membrane potential

difference in charges across cell membrane when neuron is at rest (-70mV)

How do ions cells travel in and out of the membrane

facilitated diffusion through ligand gated channels

How does K+ diffuse

tendency to diffuse out of cell

How does Na+ diffuse

tendency to diffuse into cell

compare diffusion of K+ and Na+ at rest

more K+ diffuse out of cell than Na+ diffuse into cell

relative polarity of outside and inside of cell at rest

outside is positive and inside is negative

What is an Action Potential

nerve impulse

occurs when a neuron recieves a stimulus

What happens to membrane and polarity when a neuron receives a stimulus

cause gated Na+ channels to open and K+to close —> influx of Na+ into cell —> accumulation of positive charge inside cell membrane relative to outside

Depolorization

charge reversal of membrane

What happens when overall membrane potential is positive

happen at +40mV

Na+ channels shut

k+ channels open —> restore membrane potential back to resting state

Repolarization

process of restoring membrane potential to resting state

What is hyperpolarization and why does it happen

state of excess interior negative charge

during depolarization K+ channels have delay in closing causing overshoot of K+ out of cell —> causes interior of cell membrane to become excessively negatively charged in comparison to resting membrane potential

How is hyperpolarization returned to resting membrane potential

sodium - potassium pump kicks in and pumping Na+ out of cell and K+ into cell

Refractory period

time taken for membrane potential to be restored after depolarization/repolarization

How does action potential move down neuron

from cell body to axon terminal

as one region of axon becomes depolarized, the region immediately before it begins to depolarize

in axons of myelinated neurons where are gated ion channels concentrated

Nodes of Ranvier

causes action potential to jump from node to node

Threshold level

level to which membrane potential must depolarize in order for action potential to occur

All or non response

nerve or tissue respond completely or not at all to stimulus

Synaptic Cleft

spaces between neurons or between neurons and effectors

presynaptic neuron

comes before synapse

postsynaptic neuron

comes after synapse

Where are neurotransmitters released from

vesicles

neurotransmitters

chemical messenger synthesized either locally in the axon terminal or in the cell body

Explain how neurotransmitters go form one neuron to another

vesicle combine with presynaptic end plate because both are phospholipids —> neurotransmitters released —> lock and key with receptors on postsynaptic neuron to induce electrochemical response by opening ion gated channels.

2 types of neurotransmitters

small molecule neurotransmitter: very small; sometime amino acid

Neuropeptides: larger protein complex made up of 3 or more amino acids

excitatory neurotransmitters

cause ligand gated sodium ion channel to open —> lead to membrane potential more positive —> leads to depolarization and production of an action potential down post synaptic neuron

inhibitory neurotransmitter

cause ligand-gated potassium ion channels to open —> leads to cell becoming hyperpolarized —>prevent production of an action potential down neuron

Acetylcholine

excitatory neurotransmitter; induces skeletal muscle contractions

What enzyme is used to break down acetylcholine

cholinesterase and broken down into acetate and choline

what is reuptake

process of acetate and choline taken back up the pre-synaptic vesicles

How is more acetylcholine created

choline stored and combined with acetyl CoA (from cell respiration) to produce more acetylcholine

chemoreceptors 

detect chemical change

mechanoreceptors 

detect things like stretch movement, blood pressure change

sensory neuron

supply nervous system with info about external environment and conditions of internal env

thermoreceptor

detect change in temp

epidermis

outermost layer of skin, makes contact with external env

sensory adaptation

occurs when a receptor becomes accustomed to the stimulus (habituation)

sclera

firm white outermost layer of eye

cornea

front bulging part of Sclera and bends light towards pupil

aqueous humour

fluid filled located in a chamber just behind the cornea

Choroid

very vascularized middle layer of eye

iris

circular coloured ring of muscle that controls pupil size

lens

transparent structure that focuses light on retina

ciliary muscles

controls the shape of the lens