Download Chapter 9 Nervous

Ch 9 Notes
Neuron Function
Describe the neuron, the nerve impulse, and the synapse, and explain the
components of a reflex arc
Neuron - specialized cell that lies within the nervous system; conducts electrochemical
signals along their length
body - major portion of neuron
axon - transmits signals to other structures (groups are nerves)
dendrite - receive signals from other neurons
3 Classifications of Neurons
Sensory Neurons - deliver a signal from a specialized receptor to the CNS. (force, light,
sound, chemical)
Interneurons - deliver a signal from one neuron to another
Motor Neurons - deliver the signal from the CNS to the muscle or gland being
stimulated for a response
How does it work?
Na ions are transferred out into extracellular fluid.
K ions are transferred into cell within cytoplasm.
This is threshold potential.
The permeability of the cell membrane increases, allowing Na to rush into the
cell.
Cells interior takes a positive charge. (Called depolarization)
Depolarization sweeps down the neuron, making the impulse or action potential.
Neuron immediately begins to repolarize.
K ions diffuse rapidly out of the cell.
Normal resting potential is reached.
Impulses are transmitted to other neurons by a synapse.
Neurotransmitters such as acetylcholine (ACH) help.
Brain Structure & Function
Identify the major structures of the brain and name associated functions
CNS = central nervous system; brain and spinal cord
PNS = all nerves and neurons outside brain & spinal cord; throughout the body
Cerebrospinal fluid = CSF = fluid that is produced by the brain and bathes the CNS
Brain Structure/function:
Cerebrum - largest and most prominent, controls voluntary movement and
thought (divides into 2 halves or hemispheres)
Cerebellum - provides coordination of movement
Diencephalon - hormone secreting glands; thalamus and hypothalamus
Brain stem - controls most functions necessary to maintain life (respiration)
Anatomy and Function of the Spinal Cord
Discuss the anatomy and function of the spinal cord
Spinal Cord Structure/Function - link between PNS and brain
Two nerve branches exit spinal cord at each vertebral segment (dorsal and
ventral root)
Dorsal root = carries sensory nerves.
Ventral root = motor function
Sensory Somatic and Autonomic Nervous Systems
Sensory Somatic/Autonomic Nervous System = 2 divisions of PNS
Sensory Somatic = operates all motor activity; includes receptors and neurons
associated with detecting environmental changes
Includes 12 pairs of cranial nerves that enter the brain directly; not the spinal
cord. Control functions of structures within the head mostly.
(Listed in figure 9-12 & 9-1) = NEED TO KNOW
Autonomic Nervous = divides into sympathetic and parasympathetic; involuntary
Controls internal conditions; glands, smooth muscle, cardia muscle
Sympathetic = fight or flight (pupils dilate, bronchi dilate, increase heart rate, etc)
Parasympathetic = opposite effects (slows HR, lowers blood pressure, etc)
Types of Receptors - how nervous system detects changes
Heat receptors - present in skin for external temp and within hypothalamus for
internal changes
Mechanoreceptors - detects pain and pressure. Pain is interpreted when
the neurons receive a deep stimulus.
Chemoreceptors - detect changes in water or salt concentrations, taste, smell...
Vestibular receptors - detect sound
Ocular receptors - sensitive to light; allow sight, dilation and constriction of pupils
Clinical Practice
Defects in the nervous system can be detected through physical examination.
mental status - alert, depressed, coma, head tilt
reflexes - evaluates cranial nerves
menace - bring finger rapidly towards eye
pupillary light reflex - shine light into pupil
gag reflex - finger deep into mouth
normal tongue strenth
Neurological problems:
seizures - excess firing of neurons; loss of balance to violent uncontrolled motor
activity
Listeriosis - infection seen in cattle/sheep/goats; bacteria infects brain; drooping
eyelids to paralysis
EPM (equine protozoal myeloencephalitis) - protozoa that invades brain and
spinal cord; staggering to paralysis