Physiology Exam 2

Sodium ions

Depolarization

Repolorization

The potassium channels open and the sodium channels close. (reset of the distribution of Na+ (out) and K+ (in)

Mechanoreceptors = respond to touch, pressure, vibration, stretch, and itch Thermoreceptors = are sensitive to changes in temperature Photoreceptors = respond to light energy Chemoreceptors = responds to chemicals, monitor oxygen levels and acidity levels in major blood vessels Nociceptors = sensitive to pain, causing stimuli Osmoreceptors = detect changes in concentration of solids and osmotic activity

2 potassium ions released, 3 sodium ions enter

By the frequency of action potentials

Coordinates our movements, sense the environment, and integrate senses

Central Nervous System(CNS) & Peripheral Nervous System (PNS)

Non-neuronal cells that support the functioning of neurons

Satellite cells = Surround neuron cell bodies in ganglia. Regulate O2 and CO2, nutrient, and neurotransmitter levels around the neurons in ganglia Schwann cells = Surround axons in PNS, responsible for myelination of peripheral axons, participate in the repair process after injury Oligodendrocytes = Myelinate CNS axons, provide structural framework Astrocytes = Maintain blood-brain barrier, provide structural support, regulate ion, nutrient and dissolved gas concentrations, absorb and recycle neurotransmitters, form scar tissue after injury Ependymal cells = Line ventricles (brain) and central canal (spinal cord) and assist in producing, circulating, and monitoring CSF Microglia = Remove cell debris, wastes and pathogens by phagocytosis

Ependymal cells

Schwann cells and Satellite cells

Astrocytes, Oligodendrocytes, Microglia, and Ependymal cells

Oligodendrocytes and Schwann

Microglia

Outside the cell

Inside the cell

-70mV

Because of the difference in ion concentrations found in the inside and outside of the cell

Along the length of the axon through electrical impulses

Through the release of neurotransmitters (chemically)

Calcium

1. Action potential depolarizes the axon terminal
2. The depolarization opens voltage-gated Ca2 channels and Ca2 enters the cell
3. Calcium entry triggers exocytosis of synaptic vesicle contents
4. Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell
5. Neurotransmitter binding initiates a response in the postsynaptic cell

Glutamate and GABA

Ligand-gated, Mechanically-gated, Always Open, and Voltage gated

Chemically gated = Opened by neurotransmitters Mechanically gated = Open in response to physical force Always open = Potassium channels Voltage-gated = Respond to electrical signals

Variable strength = Graded potential Constant strength = Action potential Can sum to cause an action potential = Graded potential All or none = Action potential Generated at axon hillock = Action potential Does not travel through the neuron = Graded potential Travels from dendrites to axon terminal = Action potential Intensity of stimulus coded in frequency of potentials = Action potential

Excitatory postsynaptic potential (EPSP) and inhibitory postsynaptic potential (IPSP)

Temporal summation occurs when multiple neurons stimulate a single neuron at the same time, while spatial summation occurs when a single neuron is stimulated by multiple neurons at different times.

1. Resting potential = Sodium-potassium pump (Na+/K+) maintains electrochemical gradient. Some K+ leaks out of the neuron
2. Depolarization = Voltage gated Na+ channel open. Sodium enters neuron by diffusion. Membrane potential is achieved (threshold potential)
3. Repolarization = Voltage gated K+ channel open. K+ exits out of the neuron causing membrane potential to be negative again
4. Resting potential (reset) = Distribution of Na+/K+ is reset by returning the neuron to resting potential

It pumps sodium ions out of the cell and potassium ions into the cell by active transport

2 K+ are released and 3 Na+ enter the cell

Continues Conduction = Action potential travels entire length of an axon, occurs in unmyelinated axons, travels about 1 m/Sec Saltatory Conduction = Action potential only propagated at node of Ranvier, occurs in myelinated axons, travels about 100 m/sec

The influx of Na+ ions causes the displacement of K+ ions down the axon.

By saltatory conduction via the Node of Ranvier

A stronger stimulus results in a higher frequency of action potentials

By the frequency of action potentials

Choroid Plexus

Physical support and protection

Cerebral Cortex = Ultimate control and information processing center Corpus Callosum = Axon fibers connecting two cerebral hemispheres Fornix = Acts as the major output tract of the hippocampus Hippocampus = Linked to memory Amygdala = Linked to emotion Cerebellum = Coordinates voluntary movement and balance and supports memories of such Medulla oblongata = Helps regulate breathing, heart, and blood and vessel function Spinal Cord = Pathway to neural fibers, traveling to and from brain, controls simple reflexes Pons = Involved in the control of breathing sensations, such as hearing, taste, and balance Midbrain = Motor movement, particularly movements of the eye and in auditory and visual processing Pituitary = Master endocrine gland Hypothalamus = Controls maintenance functions like eating, helps govern endocrine system, linked to emotion and reward

Holds 7 to 12 pieces of information = Short-term memory Disappears if not reinforced = Short-term memory Holds vast amount of information = Long-term memory Converted from short-term memory by a process called consolidation = Long-term memory

Smooth muscle, cardiac muscle, and glands

Preganglionic neuron and postganglionic neuron

Acetylcholine

Acetylcholine

Epiniephrine

They increase their activity

Inhibit them

little adaptation, constant firing of action potentials. examples stretch receptors, pain receptors, photoreceptors, mechanoreceptors

Transient or changing stimuli, such as smell, pressure, and touch

To release neurotransmitters onto sensory neurons

Modality

Thermoreceptors

Lateral inhibition

Nociceptors

Sense

Interceptors

Modality of the stimulus

To act as a voltage sensor and activate RYR channels

Tropomyosin is pulled away, exposing the binding sites on actin

To break down acetylcholine in the synapse

T-tubules

The muscle relaxes and returns to its resting state

RYR receptors

To sharpen contrast between activated receptor fields and their inactive neighbors

By the frequency of action potentials

They show little adaptation

To decrease the sensitivity of a receptor

It increases the heart rate

Norepinephrine

They are the sites of neurotransmitter synthesis, storage, and release

In antagonistic pairs

It is the motor neuron and all muscle fibers it innervates

It triggers muscle contraction