Transcript Motor neurons

Unit 2: Biological Basis for Behavior
Neurons:
• Sensory neurons
- afferent
• Motor neurons
- efferent
• Interneurons
• Mirror neurons – frontal lobe only
The Neuron: the basic building block (cell) of
the nervous system.
• Neurons are composed of the following
parts:
–
–
–
–
–
–
–
–
–
Axon
Soma/Cell Body
Dendrite
Myelin sheath
Terminal Branches
Terminal Buttons
Synapse
Post synaptic Dendrite
Glial cells
All or None Law: Like firing a gun
• Neuron will fire or it won’t – there is no
between
– Squeezing a trigger hard or soft?
– Turning on a light switch slow or fast?
• Neurotransmitters can be excitatory or
inhibitory:
Molecules that mimic neurotransmitters
• Mimics can also excite or inhibit
– Agonists excite
• Black widow spider bite (ACh)
– Antagonists inhibit
• Butolin (ACh)
• Heroin (endorphins)
– Why do different people experiences “highs” differently?
\
Acetylcholine (ACh)
•
•
•
•
Released by motor neurons
Regulation of attention, arousal, and memory
Enables muscle action, memory and learning
Lack/death of ACh creating neurons =
Alzheimer’s
Dopamine (DA)
• Control of voluntary movement
• Cocaine and amphetamines elevate activity at
DA synapses
• “reward pathway”
• Too little = Parkinson’s
• Too much = Schizophrenic disorders, addictive
disorders
– Dopamine hypothesis
Norepinephrine (NE)
• Alertness, mood, and arousal
• Cocaine and amphetamines elevate activity at
NE synapses
• Too little = depression
Serotonin
• Mood, hunger, sleep, and arousal
• Prozac and antidepressant drugs affect
serotonin circuits
– SSRI
• Too little = depressive disorders
GABA or gamma-aminobutryic acid
• Inhibitory transmitter
• Regulates anxiety, sleep/arousal
• Too little = insomnia, anxiety disorders,
seizures
Glutamate
• Widely distributed excitatory transmitter
• Learning and memory
• Too much = migraines or seizures
– Why do people avoid MSG?
Endorphins
•
•
•
•
Resembles opiates in structure and effects
Roles in pain relief and response to stress
Regulation of eating behavior
“Runner’s High”
Monoamines
• 3 neurotransmitters
– Dopamine, norepinephrine, serotonin
GABA and Glutamate
• Consist of amino acids
– GABA - produces only inhibitory postsynaptic
potentials (PSP)
– Glutamate – widely distributed in the brain, only
has excitatory effects
MAOI’s
• Monoamine Oxidase Inhibitor
• Antidepressants used to treat depression,
anxiety, etc
SSRI Antidepressants
• Selective Serotonin Re-uptake Inhibitor
• Anti depressant drugs (and some other illegal
drugs like cocaine)
– block the reuptake of neurotransmitters, keeping
in the synapse longer,
– intensifying their activity.
– For some depressed people that elevates their
mood.
Nerves
• Are long bundles of neurons that send and
return messages to and from the body from
the spinal column.
Neural Networks
• Neurons can communicate with hundred or
thousands of other neurons simultaneously.
• Neural networks can be built of visual,
sensory, cognitive, emotional information
drawn from throughout the brain and body.
In other words…
The brain processes the
sensory info
and decides
what to do
Sensory information
enters the body
through receptor cells
Motor nerves
receive commands
from the brain
and react
The Nervous System
•
•
•
•
Central Nervous System
Peripheral Nervous System
Somatic Nervous System
Autonomic Nervous System
– Sympathetic/Parasympathetic Nervous System
The Central Nervous System
• Brain and spinal cord
– Memory tip: Brain and spinal cord are located in
the center of the body
CNS
• 40 billion neurons
• Each having 10,000 contacts with other
neurons
• 400 trillion synapses
• One grain of sand size speck of your brain
contains 100,000 neurons
CNS – The Spine
• Reflexes – automatic responses to stimuli
• Pain example
– Sensory of heat from flame travels to spine,
interneuron in spinal cord, respond by activating
motor neurons leading to the muscles in your arm
The Peripheral Nervous System
• Sensory and motor neurons that connect the
CNS to the rest of the body
– Everything else outside the brain and spinal cord
– Memory tip: Fingers and toes lie in the outermost
areas of the body from the center, or the
periphery of the body
The Somatic Nervous System
• Part of the peripheral that controls skeletal
muscles
– Memory tip: Volunteer work is done by choice, so
the body’s voluntary actions are controlled by this
nervous system
The Autonomic Nervous System
• Part of peripheral that controls glands and the
muscles of internal organs (like the heart)
– Sympathetic division of nervous system arouses
– Parasympathetic division of nervous system calms
• Purpose to bring you back to homeostasis
The Autonomic Nervous System:
An Opponent-Process
• They work in opposition to one another
– What’s another opponent process we’ve talked
about in the past few days? (Think neural
impulse…)
The Endocrine System
• If nerves are the speedy highway of communication –
hormones are snail mail
• Endocrine system – slow chemical communication,
set of glands that secrete hormones into the
bloodstream
– Hormones: chemical messengers travel through
bloodstream and affect other tissues
– Endocrine = inside (pancreas, testes, ovaries, bloodstream)
– Exocrine = outside (salivary glands, tear glands, sweat
glands)
Hormones
• Chemical messengers (snail mail)
• Influence hunger, sex, aggression, etc
– Some are chemically identical to
neurotransmitters (like norepinephrine)
What’s the difference between a
neurotransmitter and a hormone?
• They are the same!
• The only difference is based on where they’re
manufactured
– Neurotransmitters are in neurons
– Hormones are in glands and based in the
bloodstream
The Endocrine System:
Adrenal Glands
• Autonomic nervous system gets its orders
from the adrenal glands
– Located on top of the kidneys
– Releases norepinephrine and epinephrine
• Called noradrenalin and adrenalin during flight-or-flight
response
The Master Gland:
The Pituitary Gland
• Pea sized located in the core of the brain
– It is controlled by the hypothalamus
– releases hormones that promote growth as well
as generally managing the rest of the endocrine
system
• The master gland
– For instance – the pituitary gland tells the sex glands to
release sex hormones to have… sex
Important glands and hormones they secrete
• Anterior pituitary gland
– Secretes growth hormone
• Too little produces dwarfism, too much produces
gigantism
• Posterior pituitary gland
– Secretes vasopressin and oxytocin
• Constricts blood vessels and raises blood pressure
• Oxytocin in women sparks labor during pregnancy
• Thyroid gland
– Releases thyroxin and triiodothyronine
• Increases metabolic rate, growth, and maturation
• Parathyroids
– Releases parathyroid hormone
• Increases blood calcium and decreasing potassium
• Pancreas
– Secretes insulin
• Regulates the level of sugar in the bloodstream
• Why do diabetics see the a doctor called an
endocrinologist?
• Ovaries
– Secrete estrogen
• Promotes ovulation and female sexual characteristics
• Testes
– Release androgens (testosterone is one type of
androgen)
• Produces sperm production and male sexual
characteristics