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Flashcards in Exam 2 Deck (100):
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Neuronal Pathways

Groups of neurons that influence each other's activity by communicating at neuronal synapses

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Synapse

The site or junction where electrical signals are transmitted from one cell to another cell

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Neuronal Synapse

Type of Synapse - Found between successive neurons in a neuronal pathway

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Neuromuscular Junction

Type of Synapse - found between somatic a-motor neurons and myofibers of skeletal muscles

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Neuroeffector Junction

Type of Synapse - Found between autonomic motor neurons and autonomic effectors including smooth muscle and glandular cells

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Presynaptic Neuron

Neuron that carries impulse INTO the synapse

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Postsynaptic Neuron

Neuron that carries the impulse AWAY from the synapse

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Chemical Synapse

Two cells forming the synapse are separated by a physical space called the synaptic cleft

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Synaptic Cleft

Narrow Space (bout 20-30nm) that separates the presynaptic neuron from the postsynaptic neuron (or effector)

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Neurotransmitters (NT)

ESM's released by neurons that diffuse across a synaptic cleft to stimulate or inhibit activity in a postsynaptic neuron or effector (muscle or gland).

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Neurotransmitter Receptors

Membrane proteins found on the postsynaptic neurons (or effectors) that bind a specific NT and generate a response in the postsynaptic cell

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Excitatory Postsynaptic Potential

Depolarizing graded potential that brings a postsynaptic neuron closer to the threshold for creating APS

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Inhibitory Postsynaptic Potential

Hyper polarizing graded potential that moves a postsynaptic neuron further away from the threshold for creating APS

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Summation

the process of integrating the input from multiple synapses

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Spacial Summation

Effect produced by the simultaneous release of NT from more than one (usually large number) synaptic knobs on a single postsynaptic neuron

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Temporal Summation

Effect produced by stimulation of NT release from the same presynaptic knob(s) in rapid succession on a postsynaptic neuron

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Facilitaiton

Facilitation occurs when the membrane potential of a postsynaptic neuron is held nearer to the threshold then normal but not yet above threshold

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Divergent Pathways

Pathways in which a signal entering into a section of a neuronal pathway excites a greater number of neurons leaving that section. Used for amplification and divergence into multiple tracts

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Convergent Pathways

Pathways in which signals from multiple input fibers (or multiple axons terminals from a single input fiber) come together to excite a single output fiber. With this type of pathway, spacial summation is used to get a postsynaptic neuron to fire

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Efferent (motor) neurons

Neurons that carry impulses away from the CNS out to the motor neurons

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Somatic motor neuron

Type of efferent neuron - controls skeletal muscle contraction

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Autonomic motor neuron

Type of efferent neuron - control involuntary effectors - cardiac muscle, smooth muscle, exocrine and endocrine glands and some adipose tissue

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Pupillary reflexes

Pupil diameter changes due to contraction of smooth muscle within the iris (colored part of the eye) to control the amount of light entering the eye

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Mydriasis

Dilation of pupil in response to pain, emotional excitement, and dim light. Involves contraction of radial muscle fiber of iris, which are controlled by the sympathetic division of ANS

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Miosis

Constriction of pupil in response to increased light entering pupil (pupillary light reflex) or to near vision. Constriction involves contraction of the circular muscle fibers of the iris, which are controlled by the parasympathetic division

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Sympathetic Division

"Thoracolumbar division" or "Emergency" or "Fight or Flight" division

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Parasympathetic Division

"Craniosacral division" or "Rest and Repair" or "Rest and Digest" division

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Sympathetic Chain ganglia (sympathetic trunk)

Cell bodies of many postganglionic neurons - found on both sides of the vertebral column.

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Preganglionic neurons

Long. Extend all over the body. "Cholingergic" - they secrete acetylcholine

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Postganglionic neurons

Short. Autonomic ganglia and axons extend to nearby effectors. (Parasympathetic - "Cholinergic" - secrete acetylcholine) (Sympathetic - "Adrenergic" - secrete norepinephrine)

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Parasympathetic Postganglionic

"Cholinergic" - secrete acetylcholine

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Sympathetic Postganglionic

"Adrenergic" - secrete norepinephrine)

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Epinephrine

80% of adrenaline. Catecholamines and act as neurohormones.

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Norepinephrine

20% of adrenaline. Catecholamines and act as neurohormones.

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Cholingeric Receptors

Activated by acetylcholine

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Nicotinic Receptors

Type of Cholingeric Receptor. Ligand-gated Na+ (cation) channels found at the synapses between preganglionic and postanglionic neurons

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Muscarinic Receptors

Type of Cholingeric Receptor. G-protein coupled receptors that activate produciton of intracellular messagers that control ion channel permeability or metabolic activity of the cell. Found on teh postganglionic effectos of the parasympathetic divison

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Adrenergic Receptors

Activated by binding of the catecholamines including both norepinephrine and epinephrine

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Adrenergic Receptors

Respond my strongly to neoepinephrine. Contain a1 and a2 receptors

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a2 receptors

Found in neuroeffector junctions on most sympathetic effectors.

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a2 receptors

Found in neuroeffector junction on the GI tract and pancreas

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B1 receptors

Equally responsibe to either NE or EPI. Found in neuroeffector junctions on all cardiac effectors and renin-secreting cells in kidneys

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B2 receptors

Respond most strongly to Epi. NOT found in sympathetic neuroeffector junctions.

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B3 receptors

Respond most strongly to NE than Epi. Found primarily on adipose tissue. Activation of these receptors leads to fat breakdown

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Adrenaline

Circulation will stimulate vasodilation of blood vessels in the heart, skeletal muscle and liver that contain B2 receptors

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Hormones

The regulatory chemicals made and secreted into the ECF by endocrine cells. The secreted hormone reaches its target cells through transport in the ECF (plasma and IF)

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Target Cells

Specific receptors for the hormone sent

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Trophic hormones

Hormones that regulate the release of other hormones

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Endocrines or circulating hormones

Hormones released by endocrine glands taht are carried in the blood plasma to act on distant target cells.

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Paracrines

Local hormones that act on neighboring cells

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Autocrines

Local hormones that act on the same cell that secreted them

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Neuroendocrines

Hormones released by neurons that are carries in plasma to act on distant target cells

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Steroids

Hormones that are synthesized from cholesterol

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2nd messangers

intracellular small molecules and ions that act as intracellular signals to activate various components of a signaling pathway

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Molecular switches

proteins that can be switch from an inactive state to an active state in response to an appropriate signal

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Protein kinases

Enzymes that catalyze the addition of phosphate to protein effectors to turn them "on"

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Protein phosphatases

Enzymes that catalyze the removal of phosphate from protein effectors to turn them"off"

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G-proteins

molecular switches that link plasma membrane receptors with intracellular signaling pathways

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Amplification

the effects of small amounts of hormone binding to target cells are greatly AMPLIFIED in intracellular signaling pathways; thus, allowing very small amount of hormone binding to a receptor to activate a powerful response throughout its target cell.

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Hypothalamus

major integrating link between the nervous and endocrine systems.

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Pituitary Gland

Attached to the hypothalamus by a delicate stalk-like structure called the "hypophyseal stalk or infundibulum" which contains the hypothalamo-hypophyseal tract.

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Hypophyseal stalk or infundibulum

track made up of axons extending from cell bodies in the hypothalamus to axon terminals in the neurohypophysis

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Adenohypophysis

Anterior pituitary - glandular portion consisting of secretory epithelial cells

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Neurohypophysis

Posterior pituitary - nervous portion consisting of axons and axon terminals of neurons that have their cell bodies in the hypothalamus

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Somatotropes

secrete growth hormone - type of glandular cells

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Lactotropes

secrete prolactin (PRL) -type of glandular cells

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Corticotropes

secrete primarily ACTH - type of glandular cells

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Thyrotropes

secrete thyroid-stimulating hormones (TSH) - type of glandular cells

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Gonadotropes

secrete two gonadotropins called follicle-stimulating hormone and luteinizing hormone - type of glandular cells

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Trophic hormoes

include both releasing hormones and inhibiting hormones. most are peptides

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Portal system

a system of blood vessels in which blood after passing through a capillary bed of one organ, is conveyed directly through venules or veins to a capillary bed of a second organ.

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Growth Hormone

secreted by the somatotropes of the anterior pituitary gland

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Somatocrinin

growth hormone releasing hormone or GHRH

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Somatostatin

growth hormone inhibiting hormone or GHIH

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Somatomedins

Insulin-like growth factor or GIF

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Hypersecretion

if a hormone is produced at a higher tahn normal level, the effects of that hormone are exaggerated

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Gigantism

High during the growth period and can result in humans that grow up to 8 feet tall

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Acromegaly

high after the growth period ends result in increased growth and thickening of bones like cranial bones, nose, jaw, vertebrae and other

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Hypersecretion

If a hormone is produced at a lower than normal level, the effects of the hormone are diminished

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Dwarfism

lack of production of GH or IGF leads to decreased lengthening of long bones during the adolescent growth period , which results in individuals of short stature

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Prolactin

secreted by the lactotropes of the anterior pituitary gland

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Adrenocorticotropic hormones

regulates the adrenal cortex

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Thyroid-stimulating hormone

regulates the thyroid gland

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Follicle-Stimulating hormone

a gonadotrophin that regulates the gonads

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Luteinizing hormone

a gonadotrophin that regulates the gonads

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Hypothalamo-hypophyseal tract

between the hypothalamus and neurohypophysis

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Oxytocin

Uterin contraction and milk letdown - controlled by neurohormone reflex pathways

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Thyroid follicles

consists of two lobes of glandular tissue located along trachea just below the larynx

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Colloid

substance

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Colloid

substance surrounding the follicular cells

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Parafollicular cells

cells found between the numerous thyroid follicles

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Thyroid hormones

T4 and T3

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Basal metabolic rate

resting rate of calorie expenditure by the body

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Cretinism

congenital hypothyroidism results in severely stunted physical and mental growth

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Goiter

is an enlarged thyroid gland that can be present in either hypothyroid or hyperthyroid conditions; in which the concentration of TSH increases

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Rickets

Vitamin D deficiency

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Calcitriol

made from vitamin D

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Parathyroid gland

hormone produced here

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Parathyroid hormone

essential for animal's survival

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Calcitonin

has only one minimal role in controlling in the ECF of non pregnant mammals but is a major regulator in lower vertebrates