Upload
melvyn-shelton
View
238
Download
3
Tags:
Embed Size (px)
Citation preview
THE NERVOUS SYSTEM
Divisions of the NS
• Central Nervous System (CNS)
• Peripheral Nervous System (PNS)
Fig. 11.32
Sensory vs. Motor Nerves
• SENSORY nerves: – Body CNS
• MOTOR nerves:– CNS Body
Fig. 10.2
2 Different Types of Motor Nerves
• Somatic NS– consciously controlled
effectors
• Autonomic NS– involuntary effectors
Cells of the Nervous System
• NEUROGLIAL CELLS
• NEURONS vs.
NEUROGLIAL CELLS
• Fill spaces• Provide structure• Produce myelin• Phagocytize bacteria
& cellular debris• Outnumber neurons• Can divide (mitosis)
Neuron Anatomy Overview • Dendrites Cell
body Axon Synaptic knobs at axon terminals Effector
Neuron Anatomy• Schwann cells
– type of neuroglial cell
– myelin sheath
• Nodes of RanvierFig. 10.3
Classification of Neurons
THE DIRECTION THEIR SHAPE
Fig. 10.6
Sensory, Motor, and Interneurons (Direction)
• Sensory neurons – PNS CNS
• Motor neurons – CNS PNS
• Interneurons– in between sensory and motor neurons
Fig. 10.7
Shapes of Neurons
Fig. 10.6
Neuron vs. a “Nerve”
• Neuron = a cell• Nerve = bundles of
neuron axons, and neuroglial cells bound together– outside brain/spinal
cord
Fig. 11.24
Neuron Physiology
• Sending neuron impulses = action potential– change in electrical charge in cell membrane
– depends on electrolytes• potassium (K+) and sodium (Na+)
First Things First: Creating a Resting Potential
• Protein pumps– open and close
– let ions through
• Active pumps – against a gradient
• Passive pumps– with the gradient
Fig. 10.13
Na+/K+ Pump
Resting Potential
Fig. 10.14
Action Potential
Fig. 10.15
Action Potential
A Nerve Impulse- a series of action potentials
Fig. 10.16
Computer activity
http://outreach.mcb.harvard.edu/animations/actionpotential.swf
Action Potential
Fig. 10.18
Action Potential Zoomed Out
What happens when the nerve impulse reaches the end of the axon?
• axon terminals– next to another
neuron (as shown) or a muscle or gland
• Gap called a synapse
Synapse
Fig. 10.11
The Synapse
• Neurotransmitters• Synaptic cleft• Receptors• Send a message
Fig. 10.12
Neurotransmitters
Classification of Neurotransmitters
• EXCITATORY = depolarize the next neuron
• It tells the next neuron/muscle/gland to GO
• INHIBITORY = hyperpolarize the next neuron – prevent the nerve
impulse from continuing
• It tells the next neuron/muscle/gland to STOP
Acetylcholine (ACH)
• First neurotransmitter discovered (1921)
• Mostly excitatory
• Skeletal muscle neuromuscular junctions & synapses between the brain and spinal cord
• Message = – muscles contract or
– continue sending impulses
Acetylcholine cont.
• Nicotine – Activates acetylcholine receptors– Releases dopamine (coming later…)
• Alzheimers– Memory loss, depression, disorientation,
dementia, hallucinations,death– Deficient acetylcholine
Glutamate
• Generally excitatory– helps send messages in the
brain
• Involved in learning and memory
• Alcohol inhibits glutamate receptor function
• Monosodium Glutamate (MSG) – food additive – stimulates glutamate
receptors in the taste buds
Serotonin
• Found in the brain• Primarily inhibitory• Sleep, mood and
temperature regulation• Insomnia – deficient
serotonin
• Antidepressants (Prozac, Zoloft, Paxil, etc) – “SSRI’s” or Selective
Serotonin Reuptake Inhibitors
– Serotonin accumulates in the synapse
– feel more content
• LSD blocks serotonin• MDMA releases excess
serotonin
Dopamine
• AKA “the brain reward”• Regulates emotions, moods and
subconscious control of skeletal muscle
• Nicotine– excess dopamine release
• Cocaine– blocks reuptake (leaves more in the
synapse)
• Methamphetamine – excess dopamine release
Dopamine - cont’d
• Dopamine also sends signals that help coordinate your skeletal muscle movements
• Parkinson’s Disease– deficient dopamine
production– tremors
GABA• Found in the brain• Generally inhibitory • Prevents the receptor
nerve from being overstimulated
• When it accumulates it has a sedative effect
• Valium, Xanax and Ativan work by allowing GABA to accumulate
•Huntington’s Disease – deficient GABA
Norepinephrine
• Found in the brain • Alertness, regulation of
moods• Ritalin & Adderall- increase
level of norepi and dopamine
• Strattera- increase only norepi
• Clinical depression – low norepi
Endorphins
• Flood the synaptic cleft during pain or stress – Usually inhibit neurons from firing, causing an
analgesic effect– At lower levels can excite the next neuron
• Reduces pain and makes one feel good• “Opiates” (heroin, codeine, morphine,
oxycodone, hydrocodone, etc) – bind to endorphin receptors and mimic endorphins
Anandamide• Involved in working memory, regulation of
feeding behavior, generation of motivation and pleasure
• Anandamide receptors are called cannabinoid receptors– A lot of cannabinoid receptors in the hippocampus
(short term memory), cerebellum (coordination) and basal ganglia (unconcious muscle movement) of brain
• THC (found in marijuana) mimics anandamides and binds to cannabinoid receptors
Peripheral Nervous System
• 12 pairs cranial nerves • 31 pairs spinal nerves
PNS Flow Chart
Peripheral Nervous System
Motor Sensory nerves nerves
Somatic Autonomic nerves nerves
Sympathetic Parasympathetic nerves nerves
PNS cont.• Motor nerves are divided
into– Somatic n.s.- conscious
activities
– Autonomic n.s. – unconscious activities
• Autonomic n.s is divided into– sympathetic and
– parasympathetic divisions.
PNS cont.SYMPATHETIC • “fight or flight”
responses• speeds up heart rate,
breathing and other functions vital to survival
• Digestion and other less essential functions will be slowed for awhile.
PARASYMPATHETIC • when the body is not
mobilized and active in fight or flight.
• speeds up digestion and other essential functions
• When the body is in this mode, heart rate and breathing are calm.
The Central Nervous System
• The Brain • The Spinal Cord
Central Nervous System - Spinal Cord
Figs11.5, 11.6, & 11.7
Reflexes
Fig. 11.8
Central Nervous System: The Brain• Cerebrum
– Largest part– Sensory & motor functions– Higher mental functions
(memory, reasoning, etc)• Brainstem
– Connects the cerebrum to the spinal cord
• Cerebellum– Coordinates voluntary
muscle movements• Diencephalon
– Processes sensory info
Fig. 11.15
The Cerebrum• Divided into right and left
cerebral hemispheres
• Covered by folds called convolutions/gyri and grooves called sulci (little groves) and fissures (big grooves)
• Connected by the corpus callosum
• It has a cortex: an outer covering about 2 mm thick
• Gray matter vs. white matter
The Cerebrum cont.
• The cerebral cortex is divided into LOBES which control various functions
• FPOT
Fig. 11.16 & 11.17
The Cerebrum cont.• FRONTAL LOBE –
– “Primary Motor Area”• controls voluntary
muscles
– “Broca’s Area”• motor speech
• usually L hemisphere
– Voluntary eye movement
– Concentration, planning, problem solving, analysis
The Cerebrum cont.
• PARIETAL LOBE– Sensory info: touch, taste, pressure, pain
• interpretation of sensory info, “awareness” of body
– “Wernicke’s Area”• sensory speech, understanding written & spoken
language• usually L hemisphere
The Cerebrum cont.
• OCCIPITAL LOBE – visual senses– analyzing visual patterns, combining visual
images with other info (i.e. recognizing a person)
• TEMPORAL LOBE – sensory smell and hearing – interpretation of sensory experiences
(understanding speech, reading)
Cerebral Hemispheres• Hemisphere = half of
sphere (brain)• The right side of the
brain controls the left side of the body and vice versa
• Corpus callosum
The Cerebellum
• Integrates sensory info– Balance,
coordination of skeletal muscle, posture
Brainstem• Brainstem: Connects the
cerebrum to the spinal cord– Midbrain: visual and
auditory reflex center– Pons: transfer nerve
impulses– Medulla Oblongata:
• Cardiac center- heart rate• Vasomotor center-
smooth muscle in blood vessels/blood pressure
• Respiratory center- breathing rate
• Coughing, sneezing, swallowing and vomiting reflexesFig. 11.21
Diencephalon1. Thalamus-
- Receives all sensory impulses (except smell) and relays them to the appropriate region of the cerebral cortex
2. Hypothalamus – – Maintain homeostasis
– Links the nervous system to the endocrine system
3. Pituitary & pineal glands
Fig. 11.19
Diencephalon cont.
• The limbic system is a collection of structures involved in emotional behavior and your feelings– Includes the amygdala
and hippocampus
MEMORY• Primarily occurs in the
cerebrum and the hippocampus (in the diencephalon)
• 3 main types of memory:1. Sensory memory = lasts
momentarily and involves input from senses
2. Short term memory = lasts from a few seconds or minutes to hours (varies)
Memory cont.3. Long term memory = the neurons actually
change shape (dendrites extend, more are made, etc) and connect with other neurons. Lasts days to years (varies).