Physiology Exam 2

What are the two control systems of the body?

Nervous and endocrine

What does the nervous system communicate through to regulate and control other systems?

Electrochemical impulses

Neuron

Respond to stimuli, conduct electrical activity, release chem. regulators

What are the structural classes of neurons based on?

\# of processes

Unipolar Neuron

1 process; "T"

Bipolar Neuron

2 processes

Multipolar Neuron

Many processes

Parts of the Neuron

Cell body, dendrites, axon, axon hillock (initial segment), axon terminals

What are the functional classes of neurons based on?

Direction of impulse

Interneurons (Association)

Located in CNS (brain) and integrate functions of nervous system

What structural class is an interneuron?

Multipolar

Motor Neuron

Conduct impulses FROM CNS to target organs

What structural class is a motor neuron?

Multipolar

Sensory Neuron

Conduct impulses from sensory receptors TO CNS

Oligodendrocytes

Form myelin sheaths; insulate/cover axon

What do myelin sheaths do?

Speed up conduction of electrical signals along axon

Myelin forming cells are called \_________ in the CNS.

Oligodendrocytes

Myelin forming cells are called \__________ in the PNS.

Schwann cells

What type of cell is a oligodendrocyte?

Glial cell

Neuron Resting Potential

-70 mV

What is the membrane potential established by?

Large negative molecules INSIDE the cell

Ligand Gated Channels

Opening in response to BINDING of chemical ligand to its RECEPTORS

Voltage Gated Channels

Protein channel when stimulated DEPOLARIZES (AP) membrane to threshold

What are voltage gated channels specific to?

Ions (Na+, K+)

Mechanical Gated Channel

Open when physical deformation to membrane occurs

Voltage-Gated K+ Channels

Slower to open and close

What membrane potential do voltage-gated K+ channels open at?

+30 mV

What membrane potential do BOTH voltage-gated K+ and voltage-gated Na+ channels CLOSE at?

-70 mV

What membrane potential doe voltage-gated Na+ channels open at?

-70 mV

Voltage-Gated Na+ Channels

Respond faster at threshold (-55 mmV)

Threshold

Approximate value (-55 mV) need for an action potential to occur

Strength of stimulus affects \_________ of AP and may recruit more neurons to have AP

Frequency

Action Potential

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

Depolarization (AP)

Overshoot (AP)

Repolarization (AP)

What letter is hyperpolarization (AP)?

D

Resting Potential (AP)

Stimulus of Action Potentials

Receptors (sensory)

Where on the neuron does the action potential take place?

Axon hillock/initial segment

How does an action potential happen?

Na+ in, K+ out

Absolute Refractory Period

Second stimulus will NOT produce an action potential

What causes absolute refractory periods?

Na+ channels are inactivated

Relative Refractory Period

Second action potential can happen ONLY IF stimulus strength is GREATER than usual

Why can relative refractory periods occur?

Some K+ channels still open

Action Potential Conduction

1. Depolarization of 1st AP is a stimulus for new AP
2. Each AP is separate; REGENERATED
3. Positive feedback of Na+ allows AP to travel without decrease

Myelinated Neurons

Myelin prevents Na+/K+ from moving through membrane

Saltatory Conduction

AP jumps node to node

What can synapses use to pass info?

Chemical and electrical stimuli

Synapse

Junction where impulses are transmitted form neurons and PNS

Presynaptic

Conducting signal TOWARDS synapse

Postsynaptic

Conducting signal AWAY from synapse

SNARE Complex

Proteins loosely dock vesicles

Excitatory Postsynaptic Potential (EPSP)

Opening Na+ or Ca2+ channels result in a graded depolarization

Inhibitory Postsynaptic Potential (IPSP)

Opening K+ or Cl- channels results in graded hyperpolarization

Does an IPSP increase or decrease likelihood of an action potential?

Decrease

Graded Potential

Summation and lack of refractory period; amplitude decreases as signal moves toward axon hillock

Acetylcholine (ACh)

Neurotransmitter; increased arousal, enhanced cognition

What is ACh involved in?

Muscle action, memory

Dopamine

Neurotransmitter; increased pleasure, suppressed appetite

What is dopamine involved in?

Mood, sleep, learning

Norepinephrine (NE)

Neurotransmitter; increased arousal, suppressed appetite

What is norepinephrine involved in?

Heart, intestines, alertness

Nicotinic ACh Receptors

Binding of 2 acetylcholine molecules opens a channel

Agonist of Nicotinic ACh Receptor

Nicotine

Antagonist of Nicotinic ACh Receptor

Curare

Muscarinic ACh Receptor

Binding at receptor opens ion channels using a G-protein

Monoamines (Neurotransmitter)

Synthesized from amino acids

Sensory Neurons

Receive sensory stimuli and produce nerve impulse

Modalities

Types of senses arise from different receptors

Mechanoreceptor

Mechanical deformation

Thermoreceptor

Heat/cold

Photoreceptor

Light

Chemoreceptor

Chemical composition

Nociceptor

Pain

Cortical Association Areas

Where perception occurs along with emotional/varying factors that will affect perception

Factors that Affect Perception

Receptor adaptation, emotions/experiences, lack of receptors, damaged neural pathways, drugs, mental illness, not all stimuli give conscious sensation

Phasic Receptors

Respond quickly but adjust

Tonic Receptors

Maintain response to simulus

Coding Potentials

Stimulus strength and adaptation

Rods

Responds to LOW levels of light

Cones

* Respond to BRIGHT light signals
* Red, blue, green

Glutamate

Neurotransmitter; increased learning, enhanced memory

What is glutamate involved in?

Memory and learning

Where do the optic nerves meet?

Optic chiasm

Tympanic Membrane

Air molecules push against it at same frequency as sound wave

What do pressures and movement of tympanic membrane indicate?

Pitch and volume

Bones of Ear

Malleus, incus, stapes

What do the three bones of the ear do?

Transduce sound by amplifying it through middle ear to oval window

Photoreceptors and bipolar cells only undergo \____________, they lack the \_______________ that mediate action potentials.

Graded responses; voltage-gated channels

Glutamate (Organ of Corti)

Binds and causes action potentials in neurons making up vestibulocochlear nerve

Stereocilia

Bent back and forth as sound waves vibrate

Organ of Corti Receptor Cells

Hair cells (mechanoreceptors)

Is fluid in the ear positive or negative?

Positive; more K+

Neural Pathway in Hearing

Vestibulocochlear nerve -\> brainstem (medulla oblongata) -\> thalamus (director) -\> auditory cortex

Chemical binding to specific CHEMORECEPTORS are responsible for the \_____________

Detection of taste and smell

Microvilli

Increase surface area; come into contact with chemicals

Where are taste buds located?

In bumps on tongue called papillae

Salt Taste

Sodium ions

Sour Taste

High acid (H+ ions)