Anatomy Lecture Exam 4

Concentration Gradient

Difference in electrical charges across a membrane

Neurons

Most common cells in nervous system, respond to stimuli by propagating action potential along a membrane, non-mitotic

Recepters

Sensory neurons, afferent

Association control center

Central nervous system: Brain and spinal cord

Interneurons

Integrate sensory information (input) into motor response, found in CNS, most prevalent type of neuron in the body

Effectors

Motor neurons - bring about the change, either skeletal, smooth, or cardiac muscle or glands

Central Nervous System

Brain and spinal cord - deliver information to PNS

Peripheral Nervous system

Cranial and spinal nerves that spread throughout the body

Sensory nerves

Carry impulses from the sensory receptor to the central nervous system, located primarily on the skin, somatic and visceral, AFFERENT

Somatic sensory nerves

Sensory nerves that we consciously perceive - 5 senses and proprioception

Visceral nerves

Detect stimuli that we do not consciously perceive, ie. blood pressure, blood glucose

Motor nerves

EFFERENT, carry information from CNS to effectors: muscles and glands

Somatic motor nerves

Transmit voluntary impulses to skeletal muscles (voluntary control)

Autonomic nerves

Involuntary control over cardiac muscle, smooth muscle, and glandular tissue

Parasympathetic nervous system

The division of the autonomic nervous system that calms the body, conserving its energy

Sympathetic nervous system

The division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations

Fight or Flight

Glial cells

6 different kinds (4 in CNS and 2 in PNS) of cells that play a supportive roll, mitotic

Excitability

Respond to stimuli, very sensitive

Conductivity

Respond to stimuli by producing electrical signals that are conducted to other cells

Secretion

Secrete neurotransmitters that communicate with other cells - trigger or stop response

Cell body

Part of neuron that contains the nucleus, transmits graded potentials

Perikaryon

Cytoplasm of the neuron

Nissl bodies

Clustered ribosomes and rough ER in neurons that produce tau proteins

Dendrites

Receptive segment: short small projections that extend from the cell body, unmyelinated, receive input and transfer the information to the cell body

Axon

Conductive segment: long singular projection from the cell body, connects to other neurons of muscle/gland cells, extend from axon hillock

Axon hillock

Initial segment: cone-shaped structure that connects the axon to the cell body, initiates action potential

Axoplasm

Cytoplasm of axon; contains neurofibromas, neurotubules, enzymes, organelles

Axolemma

Cell membrane of axon

Axon collaterals

Side branches of the axon

Telodendria

Transmissible segment: distal ends of axon and collaterals that contain synaptic vesicles

Synaptic knob

Distal end of telodendria that contain vesicles with neurotransmitters

Cytoskeleton

Structural network that provides support to the axon of the neuron

Neurofilaments

Intermediate filaments that aggregate to form bundles called neurofibrils

Neurofibrils

Bundles of neurofilaments that provide support for dendrites and axon

Tau proteins

Proteins that stabilize microtubules of neuron

Microtubules

Move materials between the cell body and axon

Axonal transport

Movement of organelles, nutrients, vesicles, and other materials to and from the cell body via the axoplasm

Anterograde

Transport of materials from the cell body to the axon terminal, delivers required materials to the synaptic knob

Retrograde

Transport of materials from the synaptic knob to the cell body for recycling or exocytosis

Fast axonal transport

Bidirectional (anterograde and retrograde) active transportation of materials along microtubules, powered by ATP

Slow axonal transport

Unidirectional (anterograde), uses the flow of axoplasm to transport enzymes and cytoskeleton parts to the axon terminal, doesn’t require ATP (passive)

Multipolar

Most common type of neuron

* multiple dendrites and 1 axon extend from cell body

Bipolar

One axon and one dendrite are attached to the cell body, only sensory, limited locations

Unipolar

Singular long dendrite extends from the cell body and merges with the axon

Nerve

A bundle of parallel axons in the PNS

Epineurium

Surrounds the entire nerve providing protection and support

Perineurium

Surrounds each fascicle

Fascicle

Bundle of parallel axons, synonymous with nerve

Endoneurium

Surrounds the axon of a single neuron to insulate it from surrounding axons, if the axon is myelinated is external to the myelin sheath.

Mixed nerves

Nerves extending from cranial and spinal nerves that carry both sensory and motor fibers

Electrical synapse

Uncommon form of synapse where ions flow through gap junction between the cells to transmit electricity, no delay therefore faster propagation and more difficult to modify

Synapse

Functional connection between a neuron and another neuron or an effector

Chemical synapse

Presynaptic neuron releases neurotransmitter to postsynaptic cell, NT diffuses across synaptic cleft, delay allows for modification

Synaptic delay

Time it takes for NT to diffuse and bind to receptors in chemical synapses

Astrocytes

Most abundant type of glial cell in CNS, have podocytes that anchor neurons and blood vessels in place, repair damaged neurons (limited) and help form the blood-brain barrier

Blood brain barrier

Blood vessels that selectively let certain substance enter the brain tissue and keep other substances out (toxins). Formed by peri vascular feet of asrtocytes, endothelial cells, and thickened basement membrane

\-Cocaine and methamphetamines destroy the BBB

Oligodendrocytes

Produce myelin in the CNS

Microglia

Phagocytize infectious agents, cellular debris, and harmful substances in the CNS

Ependymal cell

Ciliated cells that line the ventricles of the brain, produce and circulate CSF (cerebrospinal fluid)

Schwann cells

Produce myelin in PNS, limited capacity repair damaged axons

Satellite cells

Surround cell bodies in PNS and provide protection and support

Myelin

White lipoprotein that surrounds axon of neuron insulating it from electrical insulation and speeding up the propagation of nerve impulses, produced by oligodendrocytes and Schwann cells

Nodes of Ranvier

Unmyelinated sections of axon

\-Expose axolemma

Multiple sclerosis

Autoimmune disease that destroys myelin by attacking oligodendrocytes and Schwann cells

Pumps

Active transport: move ions against their gradient (low to high) using ATP ie. Na+/K+ pump and Ca2+ pump

Channels

Passive transport: move ions down their gradient (high to low), do not require ATP

Leaky channels

Always open, allow for diffusion of K+ and Na+

Chemically-gated ion channels

Open when neurotransmitter binds to its receptor, allows for diffusion of K+, Na+, and Cl-

Voltage-gated ion channel

Open in response to change in electrical charge across membrane (voltage), K+ and Cl- are simple either open or closed, Na+ is more complex

Na+ voltage gated channel

Has 2 gates: inactivation and activation

Resting: inactivation gate is open and activation gate is closed

Activation: both gates are open

Inactivation: inactivation gate is closed and activation gate is opened

modality gates

Open and close in response to sensory stimuli ie. Light, touch, and sound waves

Receptive segment

Contains chemically-gated ion channels: Na+, K+, Cl-

Initial segment

Voltage-gated Na+ channels and voltage-gated K+ channels

Conductive segment

Contains voltage-gated ion channels: Na+ and K+

Transmissive segment

Voltage-gated Ca2+ channels and Ca2+ pumps

Resting membrane potential (RMP)

Voltage that exists across the membrane when AP isn’t being produced, polarized at rest (extra cellular is relatively positive), -70mV

Graded potentials

IPSPs and EPSPs: short lived changes in RMP due to ion movement as a result of chemically gated ion channels, occur in receptive segment and move to the initial segment

Hyperpolarization

IPSPs: make the membrane potential more negative by opening chemically gated K+ and Cl- channels

Depolarization

EPSPs: makes the membrane potential more positive by opening chemically gated Na+ channels, rapid once threshold is met via voltage-gated Na+ channels —> +30mV

IPSP

Inhibitory postsynaptic potential, makes membrane potential more negative

EPSP

Excitatory postsynaptic potential, makes membrane potential more positive

Threshold stimulus

Minimal stimulus required to initiate an action potential: -55mV

Spatial summation

The adding together of EPSPs generated by multiple presynaptic neurons

Repolarization

Following depolarization (30mV) voltage gated K+ channels, K+ leak channels, and Na+/K+ pump restore the membrane potential to -70 mV or lower (hyperpolarization)

Refractory period

Period following depolarization and depolarization during hyperpolarization when the membrane has a limited capacity to respond to action potentials

\- ensures that the action potential is unidirectional

Absolute refractory period

Time during an action potential in which a second stimulus cannot initiate another action potential regardless of strength of the stimulus.

Relative refractory period

Second refractory period when stimulus of above average intensity (above threshold0 can initiate a second action potential

Neurotransmitters

\- synthesized by presynaptic neurons

\- released via exocytosis as a result of voltage-gated Ca+ channels

\- bind to specific receptors on postsynaptic membrane

\- receptor type determines physiologic activity

Acetylcholine

Widespread, can be excitatory or inhibitory depending on the receptor, broken down by acetylcholinesterase

Biogenic amines (monoamines)

Derived from amino acids with carboxyl group removed, catecholamines and indolamines

Catecholamines

Dopamine, norepinephrine, epinephrine synthesized from tyrosine

Epinephrine

Catacholamine: adrenaline, secreted by adrenal gland initiating a fight or flight response

Norepinephrine

Catecholamine: noradrenaline, responsible for arousal, wakening, dreaming, and mood regulation, controls heart rate during fight or flight response

Dopamine

Catecholamine: regulates pleasure and reward sensations (cocaine), effects skeletal muscle tone

Indolamines

Serotonin and histamine

Histamine

An indolamine - involved in sleep and memory

Serotonin

An indolamine - involved in sensory perception, thermoregulation, mood, appetite, and sleep, lower levels in those with depression

Glutamate

\- amino acid

\- the most common neurotransmitter in the brain; excitatory, excess is toxic, related to ALS

Gamma-aminobutyric acid (GABA)

\- amino acid

\- inhibitory: blocks Ca2+ channels; influences muscle tone; alcohol and anti-anxiety drugs increase levels

Enkephalins

\- neuropeptide

\- endogenous opioid

\- analgesic: blocks pain perception; associated with pleasure