BI 232 Test 1

Afferent

Carries signals/blood TOWARD a central organ/the CNS

Efferent

Carries signals/blood AWAY from a central organ/the CNS

Axon

Long, threadlike part of the nerve cell along which impulses are conducted from the cell body to other cells

Dendrite

Short, branched extension of a nerve cell, along which impulses received from other cells at synapses are transmitted to the cell body

Sensory

Afferent, nerve that transmits sensory information to the CNS

Motor

Efferent, carry signals from the CNS to muscles and glands, enabling voluntary movement, posture maintenance, and glandular activity

Interneuron

A neuron that transmits impulses between other neurons

glial cells

helper cells that surround and support the nervous system

CNS glial cells

Astrocytes, microglia, ependymal cells, oligodendrocytes

Astrocytes

Perivascular foot processes help maintain the chemical environment in the brain, regulate passage of molecules, buffer excess K+ ions and neurotransmitters in extracellular space

Microglia

Phagocytic cells within the CNS (local version of WBCs), remove foreign microorganisms and dead neural tissue

Ependymal cells

Form the epithelial lining of the brain cavities (ventricles) and central canal of the spinal cord

Oligodendrocytes

Form the myelin sheaths around axons in the CNS

PNS glial cells

Schwann cells, satellite cells

Schwann cells

Form the myelin sheaths around peripheral axons

Satellite cells

cover the soma of neurons in the ganglia

CNS protective coverings

• Dura mater = outer layer, thick, fibrous layer, fused to cranium

• Arachnoid mater = fibrous mesh, above subarachnoid space

  • Subarachnoid space = where CSF flows, some arteries as well

  • Arachnoid granulations = protrude into sagittal sinus, allow CSF to drain

• Pia mater = touching brain/spinal cord, follows all sulci

Ventricles

Lateral ventricles, third ventricle, fourth ventricle

Flow of CSF

lateral ventricle - (interventricular foramen) → 3rd ventricle - (cerebral aqueduct) → 4th ventricle → central canal - (medial/lateral apertures) → cisterns and subarachnoid space → out to veins (i.e. superior sagittal sinus)

neural tube

ectoderm goes through neurulation around 3 gestational weeks, and the neural plate forms (a thick line of cells along the dorsal side of the embryo), it indents and forms the neural groove and crest, and then separates into the surface ectoderm, the neural crest → spinal ganglia, and neural groove → neural tube, it then closes in the middle, zippers closed out to both ends and becomes the CNS

neural crest cells

become sensory neurons in the dorsal root ganglia, and then migrate and form the PNS

Stem cells

Split into pluripotent embryonic stem cells - 3 lines = endoderm, mesoderm, ectoderm

Endoderm

Inner cells, end up as most of the lining of the respiratory and digestive tracts (not mouth/rectum)

Mesoderm

Middle cells, end up as connective tissue - blood, muscles, bone

Ectoderm

Outer cells, end up as skin, and nervous tissue

Cerebrum

Principal and most anterior part of the brain, consists of two hemispheres, responsible for integration of complex sensory and neural functions and initiation and coordination of voluntary activity in the body

divided into lobes: frontal, parietal, occipital, temporal, insula - divided by longitudinal fissure, transverse fissure, central sulcus, lateral sulcus

cortex - only gray matter, 2-4 mm thick, 3 functional areas - motor, sensory, association = all are interneurons, each hemisphere controls contralateral side, symmetrical but lateralization of functions

cerebellum

subconscious, gets input from motor cortex and sensory info → smooths movements (precise timing/pattern), arbor vitae (white matter pattern), afferents come from proprioceptors and vestibular cortex, efferents go to motor cortex and brainstem (to influence motor neurons), possible roles in thinking, language, and emotion

medulla

blends into spinal cord at foramen magnum, decussation of motor control, autonomic reflex centers (cardiac, vasomotor, respiratory, also: vomiting, hiccup, cough, sneeze)

pons

part of the brainstem, mostly fibers (ascending and descending, also cortex to/from cerebellum)

hypothalamus

visceral control center (lots of hormones), nearby: infundibulum (to pituitary), mammillary glands (relay for olfactory)

basal nuclei

do movement planning (start, stop, intensity), reward pathways, comprised of globus pallidus, caudate, putamen, and substantia nigra in brainstem, uses dopamine

motor areas

part of the cerebral cortex, responsible for voluntary movement, posterior portion of frontal lobe

key areas:

• primary (somatic) motor cortex - on precentral gyrus, long axons directly to spinal cord = corticospinal (pyramidal) tracts, each body part has own area of cortex (somatotopy → motor homunculus)

• premotor cortex = just anterior to precentral gyrus, plans simultaneous/sequential movements - ex: playing instrument

• Frontal eye field - voluntary eye movements

• Broca’s area - left hemisphere, speech - controlling muscles, preparing to speak

sensory areas

often two areas, primary (processing), association (understanding)

areas:

• primary somatosensory cortex - postcentral gyrus, skin and proprioception (of contralateral side), sensory homunculus

• somatosensory association cortex - integrate sensory info to understand an object, ex: finding objects in pocket without visual cues

• visual areas - occipital lobe

  • primary visual cortex - posterior tip of lobe and medial portion, contralateral processing of shapes, colors, etc.

  • visual association cortex - recognize form, color, movement - ex: flowers, faces

• auditory areas - superior margin of temporal lobe

  • primary auditory cortex - interprets pitch, volume, location, does ipsilateral and contralateral processing

  • auditory association cortex - compares to memories - ex: scream, thunder, etc.

• insular cortex

  • vestibular cortex

  • gustatory cortex

  • visceral sensory area

  • primary olfactory cortex - in uncus ( most medial part of temporal lobe), afferents do not pass through thalamus

limbic system

emotional-visceral brain, output via hypothalamus, lots of connections to prefrontal cortex, we alternate whether logic or emotions leads us

amygdala - fear, aggression

hippocampus - gatekeeper to declarative memories

reticular formation

nuclei clusters along core of brainstem, includes reticular activating system = stimulates cortex to maintain alertness, controls sleep/wake transitions, filters most sensory to cortex, inhibited by: sleep centers, tranquilizers, alcohol, severe injury = coma, ex disease = narcolepsy - excitation leads to collapse, “sleep”