NOTES: CH 49 -NERVOUS SYSTEM
ORGANIZATION; THE HUMAN BRAIN
Recall…the nervous system is divided into 2 divisions:
● CENTRAL NERVOUS SYSTEM (CNS): information processing; integration
● PERIPHERAL NERVOUS SYSTEM (PNS): transmits info. to/from the CNS; plays a large role in regulating an animal’s movement & internal environment
Organization of the CENTRAL NERVOUS SYSTEM:
● consists of the BRAIN & SPINAL CORD
● BRAIN: integration; complex behavior
● SPINAL CORD: conveys info. to / from the brain; generates basic patterns of locomotion
SPINAL CORD:
● can also act independently of the brain as part of simple nerve circuits: REFLEXES!
● a reflex protects the body by triggering a rapid, involuntary response to a particular stimulus
● EXAMPLE: knee-jerk reflex
Organization of the CENTRAL NERVOUS SYSTEM:
● CEREBROSPINAL FLUID:
-formed in the brain by filtration of blood
-circulates through brain, providing nutrients & hormones; carries away wastes
-cushions the brain & spinal cord
GRAY & WHITE MATTER:
● GRAY MATTER:
-consists mainly of neuron cell bodies, dendrites, unmyelinated axons, & glia (support cells)
● WHITE MATTER:
-consists of bundled axons w/myelin sheaths (gives the white appearance)
Organization of the PERIPHERAL NERVOUS SYSTEM:
● consists of NERVES that branch out from the CNS and connect it to other parts of the body.
● includes:
SPINAL NERVES and CRANIAL NERVES
CRANIAL NERVES● mammals have 12 pairs of cranial nerves
● originate from the cerebrum & brain stem
● innervate parts of the head, neck and trunk
CRANIAL NERVES
SPINAL NERVES
● mammals have 31 pairs of spinal nerves
● originate from the spinal cord
● innervate the upper & lower limbs, neck, and trunk
SPINAL NERVES
PERIPHERAL NERVOUS SYSTEM (PNS):
● can be subdivided into the:
1) Motor system: oversees conscious (voluntary) activities (i.e. skeletal muscles);
2) Autonomic nervous system: controls unconscious (involuntary) activities (i.e. heart, stomach, intestines, glands)
AUTONOMIC NERVOUS SYSTEM
● branch of the PNS that is involuntary;
● includes 2 subdivisions:
1) SYMPATHETIC DIVISION;
2) PARASYMPATHETIC DIVISION.
● Sympathetic and parasympathetic divisions may act antagonistically (in opposition), alternately activating or inhibiting the actions of some organs, glands, etc.
SYMPATHETIC DIVISION:
● prepares the body for energy-expending, stressful, or emergency situations
EXAMPLE: during an emergency, the sympathetic division will increase the heart rate and breathing rate, etc.
PARASYMPATHETIC DIVISION:
● is most active under ordinary, restful conditions;
● counterbalances the effects of the sympathetic division
EXAMPLE: after an emergency, the parasympathetic division decreases the heart rate, breathing rate, etc.
Parts of the Brain:
● During embryonic development, 3 brain regions become evident:
1)FOREBRAIN2)MIDBRAIN3)HINDBRAIN
Brain Regions:
● Forebrain includes: cerebrum, thalamus, hypothalamus
● Midbrain● Hindbrain includes: pons,
medulla oblongata, cerebellum**the midbrain, along with the pons
and medulla oblongata form the BRAINSTEM
BRAINSTEM:
● anterior end of spinal cord; ● 3 parts that function in:
-homeostasis-movement coordination -conduction of info. to higher brain centers:
BRAINSTEM:
3 parts of the brainstem:
1) Medulla oblongata
2) Pons
3) Midbrain
1) Medulla oblongata: controls breathing, heart and blood vessel activity / dilation (and therefore blood pressure), respiratory center, swallowing, vomiting, digestion
2) Pons: regulates breathing centers in the medulla; relays impulses between the cerebrum and the medulla, and the cerebrum and cerebellum.
3) Midbrain:
● receives and sends sensory information;
● coordinates visual reflexes (eye movements with other movements)
● coordinates auditory reflexes (move the head to hear a sound more distinctly)
CEREBELLUM: ● coordination of movement; ● balance; ● hand-eye coordination
THALAMUS:
● relay center that sorts out & transmits sensory information to and from cerebrum;
● incoming information from all the senses is sorted here and sent on to the appropriate higher brain center;
● involved in regulating emotion
& arousal (wakefulness)
HYPOTHALAMUS:
important regulator of HOMEOSTASIS
contains body’s thermostat
includes centers for regulating hunger & thirst
plays role in sexual response and mating behavior
HYPOTHALAMUS: fight-or-flight response, pleasure, daily
biorhythms (“biological clock”) source of posterior pituitary hormones &
releasing hormones for anterior pituitary hormones
CEREBRUM:
divided into hemispheres (R and L)
each hemisphere divided into lobes (frontal, parietal, temporal, occipital)
each hemisphere has an outer covering of gray matter = CEREBRAL CORTEX
hemispheres are connected by white matter called CORPUS CALLOSUM
CEREBRUM – functions!
where memories are stored interprets sensory impulses arriving
from sense organs
centers for motor coordination; send motor impulses to muscles
where conscious decisions are made intelligence and personality stem from
cerebral activity language, cognition / thought / problem
solving
There are 2 functional cortical areas:
1) Primary Motor Cortex: sends commands to skeletal muscles, signaling appropriate responses to sensory stimuli
2) Primary Somatosensory Cortex:
receives and integrates signals from touch, pain, pressure, and temperature receptors;
divided into specific areas so that we can associate specific stimuli with specific parts of the body.
Nervous System Disorders:
● Schizophrenia
● Depression
● Bipolar disorder (manic-depressive)
● Drug addiction
● Alzheimer’s Disease
● Parkinson’s Disease
Schizophrenia:
Drug Addiction: