1. Introduction to Psychology
Chapter 3: The Biological Basis of Behavior

2. Nervous Tissue 2 kinds: neurons & glia Neurons:
- nerve cells – carry, process & pass electrochemical info
- most communicate w/ other neurons
- some communicate w/ muscles, organs

3. Nervous Tissue Parts of neuron – soma, dendrites & axon
Soma (body) – nucleus, cellular material
Dendrites (trees) – receive information, usually from the axons of other neurons – communicate w/ multiple cells
Axon (axle) – most neurons have one – like a fiber – sends info to another neuron (dendrite), muscle or gland

4. Nervous Tissue Axons may be branched
Healthy axons covered w/ myelin sheaths – fatty covering – holds in signal ~ plastic on electric cord – loss of myelin causes impairment, especially motor – multiple sclerosis (MS) – is loss of myelin

5. Nervous Tissue
Axon
Ends in a terminal button – bump that secretes neurotransmitters (chemicals)
Synapse (junction) – space between axon and dendrite
Exceptions – multiple axons, axon to soma

6. Nervous Tissue Glia (glue) Matrix for neurons
More glia cells than neurons, more than half the brain
Help feed and metabolize waste for neurons
Insulate neurons (myelin comes from glia)

7. Nervous Tissue Glia Workhorse of nerve tissue
May have some role in memory, learning

8. Nerve Impulse Electrochemical Neurons surrounded by ions
Ions = charged particles (sodium & potassium are +/chloride are –
Ions cross cell membranes – imbalance – more neg ions inside
Resting potential – neuron negatively charged – neuron at rest

9. Nerve Impulses
Action potential – neuron is stimulated > positive ions go into cell’s axon > cell becomes positive and “fires” its impulse
A brief change in charge along the axon
Changing back ??
Absolute refractory period – minimum time before neuron can have its next action potential – much less than 1 sec

10. Nerve Impulse
All or none law – action potential is an action potential – no light/heavy
Weak or strong stimulus will influence rate of firing

11. Synapse Space between neurons
Synaptic cleft – actual gap between button & dendrite
Presynaptic neuron – sends a signal
Postsynaptic neuron – receives a signal
Signals are neurotransmitters (chemicals)

12. Synapse Presynaptic neurons
Have neurotransmitters stored in synaptic vesicles in the buttons
Vesicles ~ bubbles – when neuron active, vesicles move to membrane of button
Vesicles attach to membrane

13. Synapse
Neurotransmitters cross membrane > pass through cleft (liquid through liquid)
Postsynaptic neuron has receptors in dendrites
Receptors/receptor sites are places where neurotransmitter can be read
Receptors very specific – usually sensitive to 1 (lock-and-key)

14. The Signal & the Synapse
Postsynaptic potential (PSP) – ability of receptor to change voltage when it receives neurotransmitter
No all-or-none rule
PSPs are strong/weak depending on strength of signal
2 types of PSP = excitatory or inhibatory

15. The Signal & the Synapse
Excitatory PSP = + ionic shift that makes it likely that likely that neuron will fire (action potential)
Inhibatory PSP = - ionic shift that makes it less likely that neuron will fire its action potential
Reuptake – after the PSP, neurotransmitter taken in by postsynaptic neuron - metabolized

16. Pruning
Synapses Δ over time – neural tissue becomes more efficient – babies/children form many synapses > cut back
Pruning – elimination of synapses to improve system > new synapses may form

17. Neurotransmitters Natural chemicals Some drugs interfere with them
Agonist – a chemical that imitates a certain neurotransmitter
Antagonist – a chemical that blocks a certain neurotransmitter
Agonists & antagonists act on receptor sites

18. Neurotransmitters Acetylcholine (ACh) 1st one discovered
Voluntary muscle action, attention, arousal, memory
Increased ACh therapy helps Alzheimer’s dz
Nicotine is agonist > stimulant
Curare is antagonist > dart poison - paralyzes

19. Neurotransmitters Monoamines
3 main types = dopamine, norepinephrine & serotonin
Dopamine (DA) – movement –when neurons break down (usually age) > may cause loss of DA > Parkinson’s dz –impaired movement, tremors, rigidity

20. Neurotransmitters Monoamines
Serotonin – sleep cycles, aggression, impulse control
Monoamines involved in mental illness
Depression > not enough serotonin & norepinephrine (NE)
Schizophrenia > too much DA activity, meds are DA antagonists

21. Neurotransmitters Monoamines
Abused drugs, especially cocaine/crack, amphetamines (speed) inc DA & NE
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Endorphins
Behave like opiates
Scientists curious why opiates work when not native to our bodies > morphine an opiate agonist > eating, stress, pleasure

22. Neurotransmitters GABA & Glutamate Amino acids
Gamma-aminobutyric acid (GABA)
Common in synapses
Only for inhibitory PSP (others do both)
Regulates sleep
Imbalance can cause epilepsy

23. Neurotransmitters Glutamate Commonly found
Only involved in excitatory PSP
Linked to learning, memory
Linked to long-term potentiation – when a specific neural path has synapses that stay excited > may be part of memory creation; schizophrenia

24. Nervous System Much still unknown 100 billion neurons in human brain
Divided – central nervous system (CNS) & peripheral nervous system (PNS)
CNS = brain & spinal cord
PNS = all nerves outside CNS, throughout the body
Nerves = bundles of axons

25. Peripheral Nervous System
System outside CNS
2 parts = somatic nervous system (SNS) & autonomic nervous system (ANS)
Somatic nervous system
- linked to sensory systems
- linked to voluntary skeletal muscles
- has 2 kinds of nerves = afferents & efferents

26. Peripheral Nervous System
Somatic nervous system
Afferent nerve fibers – carry info toward CNS
Efferent nerve fibers – carry info from CNS toward body
Nerves have both fibers

27. Peripheral Nervous System
Autonomic nervous system
Nerves connected with smooth muscle tissue (organs, like the heart, stomach), blood vessels & glands
Involuntary, visceral (guts) functions
Salivation, heartbeat, sweating
Active w emotions – fight-or-flight

28. Peripheral Nervous System
ANS divided = sympathetic & parasympathetic systems
Sympathetic branch handles emergencies > regulates breathing, digestion, bleeding
Parasympathetic branch handles normal life > conserves resources

29. Central Nervous System
CNS = brain & spinal cord
Protected by bone & cerebrospinal fluid (CSF)
CSF give nutrients
Blood-brain barrier – semipermeable membrane around brain & spinal cord that blocks most chemicals & blood from touching neural tissue

30. Central Nervous System
Spinal cord
links brain to PNS
Runs from base of head to waist
Most kinds of paralysis involve spinal cord
Brain
3 lbs
Command center
Much unknown