Chapter 2 Neuroscience & Biological Foundations
The Nervous System
Neurons
• Neurons are composed of:
– Cell body (soma): directs actions of the cell – Dendrites: extensions that receive information – Axon: extends from cell body, carries electrical potential, sends a chemical message to adjacent neurons via terminal buttons
The Action Potential
At rest, the inside of the neuron negative relative due to a higher concentration of positively charged ions outside the neuron. When stimulated, sodium channels open and positively charged sodium ions rush into the axon, depolarization a small region within the axon.
The region of depolarization causes nearby sodium channels to open. Just after the sodium channels close, the potassium channels open wide, and potassium exits the axon, repolarizing the tissue just behind the action potential.
This process continues as a chain-reaction along the axon. The influx of sodium depolarizes the axon, and the outflow of potassium repolarizes the axon.
The sodium/potassium pump restores the resting concentrations of sodium and potassium ions
http://intro.bio.umb.edu/111-112/112s99Lect/neuro_anims/a_p_anim1/WW3.htm
Myelinated Axons
Neurons are for Communicating
Synapse
Neurotransmitters
• Serotonin – affects mood, sleep, sensory perception, and other functions, may play a role in psychological disorders like depression • Acetylcholine – involved in memory, muscle action, sleep, emotions, those w/ Alzheimer’s have lower levels • Dopamine – affects movement, attention, memory, learning, plays role in addiction • Norepinephrine – affects learning, memory, emotions, eating, alertness, etc. • Epinephrine – emotions, memory storage…
Neurotransmitter molecule
Receiving cell membrane
Receptor site on receiving neuron
Agonist mimics neurotransmitter Antagonist blocks neurotransmitter
Nicotine is an acetylcholine agonist
Curare is an acetylcholine antagonist
The Nervous System
CNS = Central Nervous System PNS = Peripheral Nervous System
Peripheral Nervous System
PNS includes all nerves outside the brain and spinal cord
– Broken down into somatic and autonomic nervous systems…
• Somatic NS carries sensory messages to brain and motor commands to the muscles
Somatic Nervous System
Peripheral Nervous System
• Autonomic N.S. regulates automatic body functions (heart rate, breathing)
• Sympathetic: “Fight or Flight” • Parasympathetic: Active during digestion
Autonomic Nervous System
The Spinal Cord
Midline Brain View Lower Level Brain Structuresoldest part of the brain
3 major Brain Stem Structures: 1. Pons 2. Medulla 3. Reticular Formation
Midline Brain View
Corpus Callosum –
connects 2 brain hemispheres
Thalamus
Sensory relay area
HypoThalamus
4 F’s… Feeding, Fleeing, Fighting & Mating
CereBellum Smoothes movements
4 lobes of the cerebral cortex –
Frontal, Parietal, Occipital, Temporal (F-POT)
Frontal Lobes: Motor Control, Speech Production, Higher Functions
Broca’s Area
Phineas Gage… 1823 - 1861
4 lobes of the cerebral cortex –
Frontal, Parietal, Occipital, Temporal (F-POT)
Homonculus “Little Man”
Occipital Lobes
Summary of Hemispheric Specializations“lateralization”
Studying the Brain
• Lesion studies: a brain region is destroyed and behavior is observed
–Lesions of hypothalamus in animals --> overeating –Strokes interrupt blood flow in brain --> damage brain
Studying the Brain
• Electrical Recording: overall brain wave activity monitored by electroencephalograph (EEG) • Electrical Stimulation of the Brain (ESB)
Studying the Brain
• Imaging techniques allow the living brain to be studied for its activity during behavior
– CT scans (computed tomography) used to detect brain structure abnormalities in people w/ mental illness
meningitis
left temporal tumor
Studying the Brain
–PET scans use radioactive glucose to assess brain activity
Control
Ecstasy User
Studying the Brain
MRI Scan of Tumor in
Speech Center
–MRI scans generate 3D views of the human brain
• fMRI – faster version of MRI
MRI for Face Recognition in Normal Volunteer >