Physiology exam 2

Function and division of the nervous system

Regulate and control other systems of the body by communicating through electrochemical impulses

Afferent division

Contains somatic sensory, visceral sensory, and special sensory

Part of teh peripheral nervous system

Conducts impulse TOWARDS the CNS

Efferent division

Contains somatic and autonomic motor (sympathetic, parasympathetic, enteric)

Part of peripheral nervous system

Conducts impulse AWAY from CNS

Parts of central nervous system

Brain and spinal cord

Neuron

Respond to stimuli, conduct electrical activity, release chemical regulators

Parts of a neuron

Cell membrane, cell body (soma), dendrites, axon, oligodendrocyte, node of ranvier, myelin sheath, synapse

Association/interneurons

Located completely within CNS and integrate functions of the nervous system

MULTIPOLAR

Motor neurons

Conduct impulses from CNS to target organs (muscles or glands)

MULTIPOLAR

Sensory neurons

Conduct impulses from sensory receptors to CNS

UNIPOLAR

Glial cells of CNS

Constitute for about half the cells in the CNS

Can divide by mitosis unlike neurons

Provide physical and metabolic support

Oligodendrocytes

Insulates and covers axons

Forms myelin sheaths, speed up conduction of electrical signals along axon

Myelin forming cells called _______ are in CNS

Oligodendrocytes

Myelin forming cells are called _______ in the PNS

Schwann cells

ligand gated

Opening in response to binding of a chemical ligand to a receptor

voltage gated

Protein channel when stimulated depolarized membrane to threshold, specific to ion

mechanical gated

Open when physical deformation to membrane occurs, stretching

voltage K+

opens at 30mV

Slower to open and close

voltage Na+

opens at negative values

Responds faster to threshold (+30mV)

Breaking positive feedback loop

action potentials

used to communicate over large distances

What stimulates an action potential

receptors receive stimulus to begin to move action potential

where are action potentials on neurons

Axon hillock and initial segment

how do action potentials work

ions

Sodium goes in, potassium goes out

presynaptic neurons release

neurotransmitters

Neurotransmitter

Chemical messenger that travels across synaptic cleft

SNARE complex

group of proteins holding vesicles in certain spot in axon terminal

threshold

Approx. value needed for An action potential to occur

An approx. value where stimulus strength doesn’t matter after passing this certain point

Strength of stimulus affects frequency of action potential!

association/inter neurons

Located within CNA and integrate functions of nervous system

Sensory neurons

Conduct impulses from sensory receptors to CNS

Have an end to receive sensory stimuli and produce nerve impulse

Cell body

Motor neurons

Conduct impulses from CNS to target organs (muscles and glands)

Neurons have a mV of….

\-70

Action potential

All or nothing electrical event in a single cell where the membrane potential quickly becomes positive and returns to resting

Absolute refractory period

Second stimulus will not produce an action potential

Na+ channels inactivated

Relative refractory period

Happen only if stimulus strength is greater than usual

Magnitude of potential is reduced

Saltatory conduction

Myelinated neurons to prevent Na+ and K+ from moving through membrane

Action potential moves faster due to “leaping form node to node”

Synapses

Can use both chemical and electrical stimuli (action potential) to pass information

Junction where impulses are transmitted from neurons and into the PNS

Two types of synapses

Inhibitory or excitatory

Depends on neuro transmitter

At the post-synapse

Neurotransmitters in large amounts across synapse to ensure binding to a post synaptic receptor

Excitatory postsynaptic potential (EPSP)

Open Na+ or Ca2+ channels in graded depolarization

Brings membrane closer to potential

Graded potentials

Amplitude decreases as a signal moves towards axon hillock

Summarization and lack of refractory period

Characteristics of graded potentials, may lead to action potentials \`

Example of neurotransmitter at synapse

Acetycholine

Nicotinic ACh receptors

ACh binds at post synaptic cell

Agonist: nicotine

Antagonist” curare

Inhibitory post synaptic potential (IPSP)

Opening K+ or Cl- channels results in graded hyperpolarization

Brings membrane further from threshold (hyperpolarization)

Decreases likelihood of action potentials

Receptor potential s

Specialized cell that generates graded potentials

Stimulus

Energy or chemical activating a sensory receptor

Modalities

Types of senses

Arise from different receptors, each sensory neuron is specific to a sensation

mechanoreceptors

Mechanical deformation

I.e. touch

Thermoreceptors

Heat and cold

Photoreceptors

Light

Chemoreceptors

Chemical composition

Nociceptors

Pain

Neural pathways in sensory systems

Eyes: visual cortex

Ears: auditory cortex

Info (the coded action potential) then moves to the association area of cerebral cortex

Complex integration occurs at

Cortical association areas

Where perception occurs along with emotional or varying factors will affect perceptio

Factors that affect perception

Emotion and experiences, receptor adaption, afferent processing, lack of receptors to certain stimuli, damaged neural pathways, drugs, mental illness

Mechanoreceptors in skin

Respond to touch and pressure

Phasic receptors

Respond quickly but just as quickly adapt to stimulus

Tonic receptors

Maintain response to stimulus

Free nerve endings

Unmyelinated dendrites of sensory neurons

Light touch, hot cold NOCICEPTOR

Found around hair follicles throughout skin

Merkels discs

Expanded dendritic endings associated with 50-70 specialized cells

Sustained touch and indented depth

Found on base of epidermis

Ruffini corpuscles

Enlarged dendritic endings with open, elongated capsules

Skin stretch

Found in deep dermis and Hypodermis

Messiners corpuscules

Dendrites encapsulated in connective tissue

Changes in texture and slow vibrations

Found in upper dermis

Pacinian corpuscles

Dendrites encapsulated by concerntric lamellae of connective tissue structures

Deep pressure and fast vibrations

Found in deep dermis

Coding potentials

Stimulus strength and adaptation

Stimulus strength

Increasing the frequency of action potential

Adaptation

A decrease in receptor sensitivity

Transient receptor potential channels

Painful heat or painful cold stimulates a whole different set of channels to open in the membrane

Short times open start time is

The shape of the lens, and degree of refraction is controlled by____

Muscles

Adjustments or accommodations to distance of objects occur as _____ changes shape

Lens

Retina

Contains photopigments arranged to effective light trap

Rods

Respond to low levels of light

Cones

Respond to bright light signals

Red, blue, green

Photoreceptor and bipolar cells

Undergo graded responses, lack the voltage gated channels that mediate action potentials

______ are the first cells in the pathway where action potentials can be initiated

Ganglion cell

Glutamate

Neurotransmitter released with photoreceptors

Used for memory and learning, and sensory

EYES AND EARS

Optic nerve (cranial 2)

Meet at optic chiasm and project to many areas

Mainly THALAMUS

Other visual inputs come from

Brain stem and visual cortex

Tympanic membrane

Air molecules push against it at the same frequencies as the sound waves

Pressures and movement of the membrane indicate

Pitch and volume

Bones of ear

Malleus, incus, stapes

Transduce sound by amplifying it through middle ear to the oval window

Endolymph

Fluid in the ear

Highly positive with more K+

K+ moves down the gradient

stereocilia

Mechanoreceptor hair cells in ear

Bend back and forth as sound waves vibrate

How ear receives sound

K+ channels open and Ca2+ open

Bursts of neurotransmitters are release onto afferent neurons

Glutamate binds and causes action potential in neurons making up the vestibulocochlear nerve

Neural pathway in hearing

Vestibulochochlear nerve - Brian stem (medulla oblongata) - thalamus (director) - auditory cortex

Chemicals binding to specific _____ are responsible for the detection of Taste and smell

Chemoreceptors

Taste buds located in bumps on tongue called ____

Papillae

Microvili

Increase the surface area of taste receptors

Salt tastes

Sodium ions

Sour tastes

High acid content and H+ ions

Sweet tastes

Glucose

Bitter taste

Quinine

Umami

Amino acid glutamate

Pathways for taste go from

Glossopharyngeal nerve - medulla- thalamus- gustatory cortex (prefrontal)

Central nervous system composed of

Brain and spinal cord

CNS functions

Receives input from sensory neurons and directs activity of motor neurons

Association neurons integrate sensory information and help direct the appropriate response to maintain homeostasis

Humans are capable of learning and memory adding a layer of modification of our behaviors

Association neurons

Integrate sensory info and help direct the appropriate response to maintain homeostasis

Forebrain- cerebrum

Largest portion of the brain “iconic gray matter”

Higher mental functions

Consists of cerebral hemisphere

Speech, taste, vision, hearing, thought, memory

Cerebral cortex

Outer gray matter of cerebrum, marked by wrinkles and folds

Known ad gyri and sulci

Divided into lobes

Corpus callous

Bundle of nerves that connect the cortex layers of the left and right hemisphere

Limbic system

Emotions!

Structures at the edge/limit of the boundary between the forebrain and hindbrain that are most associated with emotional behavior and memory formation

Physically linked to the thalamus and hypothalamus (nervous to endocrine)

Aggression

Areas in the amygdala and hypothalamus