chapter 13: the brain and cranial nerves

brain

* part of CNS contained in cranial cavity
* control venter for many body functions
* much like. complex computer but more
* parts of the brain
* brainstem, cerebellum, diencephalon, cerebruh
* cranial nerves

brainstem (connects spinal cord to brain)

integration of reflexes necessary for survival

cerebellum (attached to the brainstem posterior to pons)

* involved in the control of locomotion, balance, posture
* can “learn” highly specialized motor functions through specific, repeated comparator activities
* proprioceptive neurons provide info. about location/position of the body constantly
* compares actual movement with intended movement and can correct to make movements smooth

diencephalon

* located between the brainstem and cerebellum
* components: thalamus, subthalamus, epithalamus, hypothalamus

cerebrum

constant thought, control

cranial nerves

* part of PNS, arise directly from brain
* 2 pairs arise from the cerebrum
* 10 pairs arise from the brainstem

brainstem parts

midbrain, pons, medulla oblangata

brainstem: medulla oblongata

regulates: HR, BV diameter, respiration, swallowing, vomiting, hiccuping, coughing, sneezing

brainstem: pons

* sleep center (initiates REM)


* respiratory center coordinates with center in medulla

brainstem: midbrain

hearing, visual reflexes, turn eyes/head, visual tracking of moving objects, unconscious regulation and coordination of motor activities

* small

thalamus

* serves as a relay center for sensory and motor impulses between the spinal cord and medulla oblongata, and the cerebrum


* it recognizes sensory impulses of **heat, cold, pain, pressure, etc.**

frontal lobe

* voluntary motor function, motivation, aggression, sense of smell, mood, personality, decision making

parietal lobe

reception and evaluation of sensory information except smell, hearing, and vision

occipital lobe

reception and integration of visual input

temporal lobe

reception and evaluation of smell and hearing; memory, abstract thought, judgement

insular lobe

deep, taste (sometimes called the 5th lobe)

cerebrospinal fluid (CSF)

* similar to serum, but most protein removed
* bathes brain and spinal cord
* protective cushion around CNS
* blood-cSF barrier

blood-cerebrospinal fluid barrier

* endothelial cells of capillaries attached by tight junctions
* substances do not pass between cells
* substances must pass through cells
* makes the barrier very selective

blood supply to the brain

* brain requires a tremendous amount of blood
* receives 15-20% of blood pumped by heart
* interruption can cause unconsciousness and irreversible brain damage
* high metabolic rate; dependent upon constant supply of oxygen and glucose
* blood-brain barrier

blood-brain barrier

* capillary endothelial cells along with astrocytes and basement membrane
* to be considered when developing drugs

cranial nerves

* indicated by roman numerals I-XII from anterior and posterior
* may have one or more of 3 functions

3 functions of cranial nerves

sensory, somatic motor, parasympathetic

sensory

special or general

somatic motor

* control of skeletal muscles
* proprioception (position of various body parts, including joints and muscles (input to brain))

parasympathetic function of cranial nerves

regulation of glands, smooth muscles, cardiac muscle

olfactory

smell

optic

vision

vestibulococholear

hearing and balance

trochlear

eye muscles

abducens

eye muscles

accessory

neck, throat, shoulder

hypoglossal

tongue

trigeminal

facial muscles and receptors

oculomotor

eye muscles (pupil dilation)

facial

facial muscles and receptors

glossopharyngeal

mouth and throat

vagus

digestion, heart rate, etc.