Human AP exam #4

Synapses

Synapses

small spaces between neurons that are important centers for the transmission of electrochemical messages

Neurotransmitters

the carriers of these messages are biological messenger molecules

Sensory receptors

gather information by detecting changes in the environment

Nucleus

is near the center of the cell body and has a conspicuous nucleolus

Dendrites

usually high branched, providing receptive surfaces to which processes from other neurons communicate

Unmyelinated axons

the smallest axons also have Schwann cells enclosure, but they do not wind around them, so they lack a myelin sheath

-appear grey

Myelinated axons

axons with a myelinated sheath

-appear white

Sensory neurons

afferent neurons- carry nerve impulses from peripheral body parts into the CNS

Interneurons

association or internuncial neurons- lie within CNS, are multipolar and form links between other neurons

Motor neurons

efferent neurons- are multipolar and carry nerve impulses out of the CNS to effectors

Accelerator neurons

increase muscular activities

Inhibitory neurons

decreases muscular activities

Astrocytes

star-shaped cells- provide support and hold structures together

Oligodendrocytes

form myelin in the CNS, can send out a number of processes so that one cell can provide myelin for many axons

Microglia

are small and have fewer processes than other neuroglial cells, help support neurons and phagocytize bacterial cells and cellular debris

Ependymal

cuboidal or columnar cells that may have cilia, form the inner lining of the central canals, covers the inside of the ventricles, help regulate the composition of cerebrospinal fluid within the ventricles

Chemically gated

ion channels are opened or closed by this reaction

Synaptic potentials

created by chemically gated ion channels enable one neuron to influence another

Potential difference

the difference in the electrical charge between the two regions

Membrane potential

the potential difference across the membrane

-measured in millivolts

Resting potential

the membrane potential of a resting neuron and has a value of - 70mV

Hyperpolarized

if the membrane potential becomes more negative

Depolarized

if the membrane potential becomes more positive

Repolarization

slower voltage-gated potassium channels open, potassium diffuses outward and the inside of the membrane becomes negative again

Nerve impulse

a series of action potentials along an axon

Refractory period

following passage of a nerve impulse, a threshold stimulus will not trigger another impulse on an axon

Absolute refractory period

lasts about 1/2500 of a second- the membrane is changing in sodium permeability and cannot be stimulated

Relative refractory period

when the membrane is reestablishing its resting potential- a threshold stimulus of high intensity may trigger an impulse

Saltatory conduction

myelinated nerve fibers have action potentials occurring only at the nodes of Ranvier- they appear to jump from node to node

Acetylcholine

stimulates skeletal muscle contractions

Monoamines

formed by modifying amino acids

Acetylcholinesterase

decomposes acetylcholine

Reuptake

other neurotransmitters are transported back into the synaptic knob of the presynaptic neuron

Monoamine oxidase

inactivates epinephrine and norepinephrine after reuptake

Enkephalins

consist of a chain of 5 amino acids. Synthesized during periods of painful stress.

Beta endorphin

found in the brain and cerebrospinal fluid

Substance P

consists of 11 amino acids and is widely distributed throughout the nervous system

Forebrain

prosencephalon

Midbrain

short section between the diencephalon and pons. -mesencephalon

Hindbrain

rhombencephalon

Frontal lobe

bordered posteriorly by a central sulcus and inferiorly by a lateral sulcus

Parietal lobe

separated from frontal lobe by central sulcus

Temporal lobe

separated from frontal and parietal lobes by lateral sulcus

Occipital lobe

separated from cerebellum by a shelflike extension of the dura mater called the tentorium cerebelli

Insula

island of Reil- located deep within central sulcus- separated from the frontal, parietal, and temporal lobes by a circular sulcus

1. may serve as a crossroads for translating sensory information into appropriate emotional responses- such as feeling disgust at the sight of something unpleasant

Primary motor areas

lie in precentral gyri of the frontal lobes; contain many large pyramidal cells

Reticulospinal and rubrospinal tracts

coordinate and control motor functions that maintain balance and posture- many of these pass into the basal ganglia

Broca's area

just anterior to the primary motor cortex and superior to the lateral sulcus, usually in the left hemisphere

Frontal eye lid

controls voluntary movements of the eyes and eyelids

General interpretive area

plays the primary role in complex thought processing- receives input from multiple sensory areas and consolidates the information which is then communicated to other brain areas

Corpus callosum

transfer sensory information from the nondominant to the general interpretative area of the dominant

Memory consolidation

the conversion of short-term memories into long-term memories

Long-term synaptic potentiation

frequent, nearly simultaneous, and repeated stimulation of the same neurons, primarily in the hippocampus, strengthens their synaptic connections

Infundibulum

a conical stalk behind the optic chiasma to which the pituitary gland is attached

Posterior pituitary gland

hangs from the floor of the hypothalamus

Mammillary bodies

two rounded structured behind infundibulum which serve as relay stations for olfactory pathways

Pineal gland

produces the hormone melatonin

Limbic system

composed of portions of the cerebral cortex in the medial parts of the frontal and parietal lobes connecting with the hypothalamus, thalamus, basal nuclei, and other deep nuclei

-guides a person into behavior that might increase the chance of survival

Brainstem

connects the brain to the spinal cord

Cerebral peduncles

include the corticospinal tracts and are the main motor pathways between the cerebrum and the lower parts of nervous system

Corpora quadrigemina

four nuclei on the superior surface of midbrain

Cerebral aqueduct

connects the third and fourth ventricle

Red nucleus

near the center of the midbrain and communicates with the cerebellum and with centers of the spinal cord

Pons

appears as a rounded bulge on underside of midbrain- separates the midbrain from the medulla oblongata

Medulla oblonglata

an enlarged continuation of the spinal cord, extending from the level of the foramen magnum to the pons

Nucleus gracilis and nucleus cuneatus

receives sensory impulses from fibers of the fasciculus gracilis and fasciculus cuneatus and pass them on to the thalamus or the cerebellum

Cardiac center

increases or decreases the heart rate

Vasomotor center

constrict blood vessels to raise blood pressure; dilates blood vessels to lower blood pressure

Respiratory center

acts with centers in the pons to regulate the rate, rhythm, and depth of breathing

Reticular formation

a complex network of nerve fibers associated with tiny islands of gray matter; extends from the superior portion of the spinal cord into the diencephalon; connects centers of the hypothalamus, basal nuclei, cerebellum, and cerebrum with fibers in all major ascending and descending tracts.

Cerebellum

a large mass of tissue located inferior to the occipital lobes of the cerebrum and posterior to the pons and medulla

Vermis

connects the two hemispheres at the midline

Arbor vitae

a cut into the cerebellum reveals a treelike pattern of white matter

Cerebellar peduncles

communicates with other parts of CNS by three pairs of nerve tracts

Cervical enlargement

a thickening in the neck region that supplies nerves to the upper limbs

Lumbar enlargement

a thickening in the lower back that gives off nerves to the lower limbs

Central canal

continuous with the ventricles of the brain- filled with CSF

Reflex arcs

carry out the simplest responses- reflexes

Reflex center

sensory neuron leads to several interneurons within the CNS

Spinal reflexes

reflexes whose arc passes through the spinal cord

Fasciculus gracilis and fasciculus cuneatus

posterior funiculi; carry sensory impulses from the skin, muscles, tendons, and joints to the brain - interpreted as sensations of touch, pressure, and body movements

Spinothalamic tracts

lateral and anterior tracts located in the lateral and anterior funiculi; impulses cross over in the spinal cord

Spinocerebellar tracts

posterior and anterior tracts lie near the surface of the lateral funiculi; fibers in posterior remain uncrossed; anterior fibers cross over in the medulla

Corticospinal tracts

lateral and anterior tracts occupy the lateral and anterior funiculi; most over lateral tract fivers cross over in medulla; some of anterior fibers cross over at various levels of spinal cord

Reticulospinal tracts

lateral tracts are in lateral funiculi, anterior and medial tracts are in the anterior funiculi; some fibers of lateral cross over

Rubrospinal tracts

pass through lateral funiculi; cross over in brain

Peripheral nerve

consists of connective tissue surrounding bundles of nerve fibers

Epineurium

the outermost layer

General somatic efferent fibers

motor impulses from CNS to skeletal muscles and stimulate them to contract

General visceral efferent fibers

motor impulses from CNS to various smooth muscles and glands associated with internal organs, causing certain muscles to contract or glands to secrete

General somatic afferent fibers

sensory impulses to CNS from receptors in skin and skeletal muscles

General visceral afferent fibers

sensory impulses to CNS from blood vessels and internal organs

Special somatic efferent fibers

motor impulses to the muscles used in chewing, swallowing, speaking, and forming facial expressions

Special visceral afferent fibers

sensory impulses to the brain from the taste and olfactory receptors

Special somatic afferent fibers

sensory impulses to the brain from the receptors of sight, hearing, and equilibrium

Ophthalmic division

impulses to the brain from surface of eye, tear gland, and skin of anterior scalp, forehead, and upper eyelid