Download NOTES FOR CHAPTER 13

NOTES FOR CHAPTER 13
THE NERVOUS SYSTEM
Case Study on Multiple Sclerosis..
I. Introduction
A. the nervous system is the ultimate coordinator of homeostasis
B. two parts to the nervous system:
1. central nervous system = brain and spinal cord
* these two interpret sensory information and coordinate
a response
2. peripheral nervous system = nerves that carry messages coming in to
and going away from the CNS
** these two systems work together and are connected
II. Functions of the Nervous System
1. Receives sensory input (PNS) from nerves connected to sensory receptors
2. Integration (CNS) “thinking” in the brain and spinal cord
3. Generates motor output (PNS) sending messages through nerves to effectors
III. Nervous Tissue (2 types of cells = neurons and neuroglia)
A. Neuron structure: three parts of a neuron are...
1. dendrites
2. cell body
3. axon
State the function of the sensory neuron: (PNS)
State the function of the interneuron: (CNS)
State the function of the motor neuron: (PNS)
B. Myelin Sheath covers some axons in the PNS and CNS
* myelin is a lipid substance that insulates and protects neurons
* myelin also helps with nerve healing
* the disease, multiple sclerosis (MS) develops when the myelin
sheath becomes hardened and interferes with nerve conduction
- it is an autoimmune disease
* leukodystrophy disorders are similar but their cause is genetic
C. The Nerve Impulse is an electrochemical signal passed along the neurons
It is electrical because….
It is chemical because….
1. Resting Potential – the inside of the axon is neg. compared to outside
* sodium-potassium “pump” maintains this difference at rest
Polarized!!
2. Action Potential – rapid change in polarity across the membrane when
the impulse occurs. (all or none)
* threshold =
Depolarized!!
3. Refractory Period – the membrane is restored to its resting potential
Repolarized!
D. Transmission Across a Synapse (page 288, fig. 13.4)
synapse = space between the axon of a neuron and the dendrites or cell body of
another neuron (also between axons and muscle cells)
neurotransmitter = chemical stored at the ends of axons that is responsible for
transmission across a synapse (can stimulate or inhibit responses)
* at least 100 known
* examples are acetylcholine (ACh) and norepinephrine (NE)
integration = the sum of inhibitory and excitatory signals received by a neuron
(threshold or not ??)
* drugs that affect the nervous system can... (page 304)
1. promote action of neurotransmitters
2 decrease the action of the neurotransmitter
3. mimic or replace the neurotransmitter
III.
The Central Nervous System (brain and spinal cord)
A. Protectors of the CNS are...
1. skull and vertebrae
2. meninges
3. cerebrospinal fluid (CSF)
* meningitis
* hydrocephalus
CNS has gray matter and white matter... difference?
B. Spinal Cord has pairs of spinal nerves (PNS) which leave between vertebrae
- because the white matter tracts cross as they enter the brain...
- functions of spinal cord
1. communication between brain and PNS
2. center for reflex arcs (internal and external)
C. Brain (page 293)
1. Cerebrum – largest part of human brain (divided into two sides or hemispheres)
a. Cortex is gray matter for integration
- sensory input and motor output
- learning, memory, language
* lobes are named the same as the skull
* association areas are places where integration occurs
b. Central white matter is “wiring”
- connected by corpus callosum
Parkinson Disease – basal nuclei are over active due to lack of the neurotransmitter
dopamine
- cells making dopamine are being destroyed (autoimmune disease)
- gradual loss of motor control
2. Diencephalon - hypothalamus helps maintain homeostasis and
controls the pituitary gland (links nervous and
endocrine systems)
- thalamus receives sensory information and sends it
to the proper area of the cerebrum, also memory
and emotions (gray matter)
- pineal gland releases melatonin
3. Cerebellum
- maintains posture and balance
- muscle coordination
- rote muscle memories
4. Brain Stem - midbrain acts as a relay station and reflex center
- pons “bridge” between cerebellum and the rest of the
CNS and breathing and reflex head
movements
- medulla oblongata is basic life support center (heart rate
Breathing, blood pressure)
* also reflexes like coughing, sneezing, etc.
- reticular formation regulates alertness (severe coma if damaged)
* anesthetics often work here
IV.
The Limbic System and Higher Mental Functions & Emotions
A. Limbic System – blends primitive emotions with higher mental functions
- a series of tracts that run through the cerebrum and diencephlalon
Alzheimer’s disease affects this part of the brain first
affecting short term memory
B. Memory is the ability to hold a thought or recall events
1. short-term memory
2. long-term memory is a mix of semantic (numbers, words, etc.) and
episodic memories (persons, events, etc.) NEED BOTH
3. Skill memory helps us do automatic motor activities like...
Learning is retaining and using past memories !!!
* check out Amnesia on page 298
C. Language and Speech are combinations of recall, knowing what and how to
say something and actually forming the words – all different parts of the
brain.
* involves processing centers like Wernicke’s area and Broca’s area
Left Brain
Right Brain
= verbal, logical, analytical, rational
= nonverbal, visuo-spatial, intuitive, creative
13.4
The Peripheral Nervous System
A. Nerves are bundles of axons, they can be sensory (incoming) or
motor (outgoing) from the CNS or a mixture of these
B. Cranial nerves (12 pair) are connected directly to the brain
they carry messages to sense and activate things like....
C. Spinal nerves (31 pair) are connected to the spinal cord
they carry messages to sense and activate things like...
D. Somatic System is the voluntary and muscle reflex part of the PNS
- it receives sensory information and takes messages to skeletal muscles
Reflex = a rapid, involuntary response to a stimulus
Reflex Arc...
Parts…(locate on the diagram on page 301 in your book)
a. sensory receptor
b. sensory neuron
c. interneuron
d. motor neuron
e. effector (muscle or gland)
A stimulus is received by a _________________________, which initiates an impulse
in the __________________________. The impulse travels through the sensory neuron
to the spinal cord and transmits it to the __________________________. This neuron
passes the impulse to the _______________________________, whose axons take the
message to an _________________________ which reacts to the stimulus.
E. Autonomic System controls cardiac muscle, smooth muscle and glands
- system is divided into sympathetic and parasympathetic divisions
Sympathetic = “emergency response”
Parasympathetic = “normal”
- both function automatically
- both have nerves in all internal organs
- both control reflexes involving homeostasis
Comparison on page 302
V.
Drug Abuse (drugs can cause physical dependence and withdrawal)
A. Alcohol
– metabolized in the liver (damage from fat build up = cirrhosis)
- brain cells die when exposed to too much alcohol
- CNS depressant (decreases activity at synapses)
B. Nicotine
- excess of neurotransmitter dopamine (mood) and mimics ACh
- stimulant
- complications in pregnancy
C. Caffeine
- a CNS stimulant affecting many neurotransmitters
- increases metabolism in the brain but decreases blood flow
D. Cocaine
- prevents uptake of dopamine so stimulation is constant
- body stops making its own neurotransmitters so the “crash”
- greater risk of stroke and heart attack
E. Methamphetamine - keeps neurotransmitters in synapses  stimulation
- causes agitation, wakefulness and psychosis
- tolerance increases with addiction
F. Heroin
- opium derived as pain medication (depressant)
- mimics the endorphins or “feel good” chemicals of brain
- body stops making its own so withdrawal is extreme
G. Marijuana - wide ranging neurological effects, some dependence
- mimics a neurotransmitter
VI.
Homeostasis
A. the nervous and endocrine systems are most important in maintaining
homeostasis
nervous system
peripheral nervous
system
central nervous
sytem
brain
"nerves"
spinal cord
somatic nervous
system
autonomic nervous
system
voluntary: skeltal
muscles
involuntary:cardiac,
smooth and glands
sympathetic emergency
parasympatheti normal