Human Anatomy and Physiology Chapter 11 Pearson

Nervous System
Master Controlling and communicating system of the body, cells communicate via electrical and chemical signals, rapid and specific, usually cause almost immediate responses.

Nervous system functions
Sensory input, Integration (brain), and motor output

Central Nervous System
Brain and Spinal cord, Integrative and control centers.

Peripheral nervous system
Cranial nerves and spinal nerves, communication lines between the CNS and the rest of the body. (broken down into 2 divisions, afferent and efferent)

Sensory (afferent) division
somatic and visceral sensory nerve fibers conducts impulses from receptors to the CNS

Motor (efferent) division
motor nerve fibers, conducts impulses from the CNS to effectors (muscles and glands) split up into two systems, somatic and autonomic

somatic nervous system
somatic motor (voluntary), conducts impulses from the CNS to skeletal muscles

Autonomic nervous system (ANS)
Visceral motor (involuntary) conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands ( split in two divisions sympathetic and parasympathetic)

Sympathetic Division
mobilizes body systems during activity

Parasympathetic Division
Conserves energy, promotes house keeping functions during rest

Histology of nervous tissue
Highly cellular; little extracellular space, tightly packed (Two cell types Neuroglia and Neurons)

Neuroglia
small cells that surround and wrap delicate neurons

Neurons
excitable cells that transmit electrical signals, structural units of the nervous system, large highly specialized cells that conduct impulses, extreme longevity 100+ years, amiotic with few exceptions, high metabolic rate and requires continuous supply of oxygen and glucose, all have cell body and one or more processes

Astrocytes
The most abundant CNS neuroglia, functions include support and brace neurons, play role in exchanges between capillaries and neurons, guide migration of young neurons, control chemical environment around neurons, respond to nerve impulses and neurotransmitters, influence neuronal functioning (participate in information processing in brain)

Microglial cells
Defensive cells in the CNS, migrate toward injured neurons, can transform into phagocytize microorganisms and neuronal debris

Ependymal cells
Line cerebrospinal fluid filled cavities, may be cilitated, cilia beat to circulate CSF, line the central cavities of the brain and spinal column, form permeable barrier between cerebrospinal fluid (CSF) in cavities and tissue fluid bathing CNS cells

Oligodendrocyte
have processes that form myelin sheaths around CNS nerve fibers

Satellite cells (Schwann cells)
Form Myelin and surround neurons in the PNS, surround all peripheral nerve fibers and form myelin sheaths in thicker nerve fibers, similar function as oligodendrocytes, vital to regeneration of damaged peripheral nerve fibers

Multipolar neurons
Most abundant in body. Major neuron type in CNS.Most multipolar neurons are interneurons that conduct impluses winthin the CNS, integrating sensory input or motor output. May be one chain of CNS neurons, or a single neuron connecting sensory and motor neurons. Some multipolar neurons are motor neurons that conduct impulses along efferent pathways from CNS to an effector (muscle/gland) Ex. Purkinje cell of the cerebellum and pyramidal cell.

Bipolar neurons
Rare. Found in some special sensory organs (olfactory mucosa, eye, ear) Essentially all bipolar neurons are sensory neurons that are located in some special sense organs. For example bipolar cells of the retina are involved in transmitting visual inputs from the eye to the brain via an intermediate chain of neurons. Ex. olfactory cell and retinal cell.

Unipolar neurons
Found mainly in the PNS. Common only in dorsal root ganglia of the spinal cord and sensory ganglia of cranial nerves. Most unipolar neurons are sensory neurons that conduct impulses along the afferent pathways to the CNS for interpretation (These sensory neurons are called primary or first-order sensory neurons) Ex. Dorsal root ganglion cell.

Graded potentials
Incoming signals operating over short distances. Short-lived localized changes in membrane potential. Magnitude varies with stimulus strength. The stronger the stimulus the more voltage changes and the farther the current flows. Either depolarization or hyperpolarization. Triggered by stimulus that opens gated ion channels. Current flows but dissipates quickly and decays. Are always over short distances.

Action potentials
Principal way neurons send signals. Principal means of long-distance neural communication. Occur only in muscle cells and axons of neurons. Brief reversal of membrane potential with a change in voltage of 100 mv. Do Not decay over distance like graded potentials

Hyperpolarization
when K+ ion channels open and many K+ rush out and the cell becomes more negative inside than it is at its resting potential

Refractory period
the time following an action potential during which a new action potential cannot be initiated

Ventricles of the brain
filled with cerebrospinal fluid, lined by ependymal cells and connected to one another and to the central canal of spinal cord

Lateral ventricles
paired; one deep within each cerebral hemisphere; large C-shaped chambers that reflect the pattern of cerebral growth; each ventricle communicates with third ventricle

Third ventricle
The midline ventricle that conducts cerebrospinal fluid from the lateral ventricles to the fourth ventricle. In diencephalon

Fourth ventricle
The passageway within the pons that receives cerebrospinal fluid from the third ventricle and releases it to surround the brain and spinal cord. In hindbrain

Septum pellucidum
anteriorly separates lateral ventricles in cerebral hemispheres

lateral aperture
Holes in 4th ventricle that allowes CSF to pass through. Also called Foramina of Lushke

median aperture
A pore in the wall of the 4th ventricle which CSF escapes out of and is led into the subarachnoid space.

thalamus
the brain’s sensory switchboard, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla

basal nuclei
Influence muscle movement, role in cognition and emotion, regulate intensity of slow or stereotyped movements, filter out incorrect/inappropriate responses, and inhibit antagonistic/unnecessary movements

broca’s area
controls language expression-an areaa of the frontal, usually in the left hemisphere, that directs the muscle movements involved in speech

hypothalamus
a neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion

limbic system
a doughnut-shaped system of neural structures at the border of the brainstem and cerebral hemispheres; associated with emotions such as fear and aggression and drives such as those for food and sex. Includes the hippocampus, amygdala, and hypothalamus.

reticular formation
A network of nerve fibers located in the center of the medulla that helps regulate attention, arousal, and sleep; also called the reticular activating system

medulla oblongata
contains centers that control several visceral functions, including breathing, heart and blood vessel activity, swallowing, vomiting, and digestion.

pons
part of the brain involved in sleep regulation also connects a cerebellum to the cerebral cortex; sleep and wake cycles

gyrus
ridge

sulcus
shallow groove

fissure
deep groove

epidural space
cushion of fat and network of veins in space between vertebrae and spinal dura mater

Dorsal horns
inter neurons that receive somatic and visceral sensory input

Ventral horns
some inter neurons; somatic motor neurons axons exit cord via ventral roots

Lateral horns
(only in thoracic and superior lumbar regions) sympathetic neurons

Dorsal roots
sensory input to cord

Dorsal root ganglia
cell bodies of sensory neurons