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Nervous System and Animal Behavior

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  1. Nervous System and Animal Behavior What factors influence behavior? How does evolution influence behavior? Explain examples of learned vs. innate behaviors?

  2. Compare and contrast Bird brains and human brains

  3. The Nervous System • The nervous system receives and interprets signals • Neurons – specialized cells that receive and respond to stimuli • Nerves – bundles of neurons

  4. The Nervous System

  5. The Nervous System 3 categories of neurons: • Sensory neurons carry information to the CNS • Motor neurons carry information away from CNS toward effector tissue • Interneurons are located between sensory and motor neurons

  6. Sensory receptors – detect sensory input • These are neurons or other cells that communicate with sensory neurons • They detect changes in conditions inside or outside the body

  7. The spinal cord also is a reflex center • Reflexes – automatic responses to stimuli • Reflex arc – prewired circuit of neurons • Sensory neuron receiving stimulus • Interneuron transmitting information • Motor neuron sending message to muscle • Reflexes allow a person to react quickly to dangerous stimuli • Withdrawal reflex – when touching something hot • The pain stimulus travels from the spinal cord to the brain and takes a little longer than the reflex • You have removed your hand from the heat before you feel the pain

  8. 21.2 The Brain • The brain is where decisions are reached and bodily activities are directed and coordinated • The human brain is roughly the size of a small cantaloupe

  9. The Brain • The brain is housed in the skull and sits inside a liquid bath called the cerebrospinal fluid for protection and cushioning

  10. Cerebrum • Largest part of brain • Contains many folds and bumps • Sulci vs. gyri • Corpus callosum is found b/t the L and R • Responsible for reasoning, intellectual fxn and critical thinking

  11. Regulates balance body position Posture Muscle coordination cerebellum

  12. Brain Stem • Midbrain • Pons • Medulla oblongata

  13. Medulla oblongata • Vital Reflex center • Visceral activities: • blood pressure, respiratory • cardiac • Part of the brain stem • Injuries often fatal

  14. Pons • b/t midbrain and medulla oblongata • Regulates rate and depth of breathing • Homeostatic mechanisms

  15. Cerebrum There are 2 hemispheres, each divided into 4 lobes • The temporal lobe involved in auditory and some visual information; memory and emotion • Occipital lobe processes visual information from eyes… • Parietal lobe processes information from touch; self-awareness • Frontal lobe processes involuntary muscle movements; planning and organizing future expressive behavior

  16. Cerebral cortex – wrinkled outer surface • If unfolded, a human cerebral cortex would be the size of a 16’ pizza • Lots of surface area in a small space • Fissure – deep groove dividing the cerebrum and cortex • Divided into right and left cerebral hemispheres • Corpus callosum – bundle of nerve fibers at base of fissure – linking two hemispheres

  17. The Brain • Functions of the brain are divided between the right and left hemispheres • The left hemisphere controls the right half of the body • The right hemisphere controls the left half of the body • The left hemisphere controls speech, reading and ability to solve mathematical problems • The right hemisphere controls spatial ability and musical and artistic creation

  18. Cerebellum, cerebrum, or brain stem • Medulla oblongata located here. • Regulates balance • Cerebral cortex is located here • Capacity for intellectual function resides here • Breathing rate is regulated here • Has folded layers with bumps and grooves • Regulates posture • Contains the corpus collosum • Pons located here • Leads to spinal cord

  19. Neuron Structure • Neurons are highly specialized cells that usually don’t divide • Damage to neurons can’t be repaired by cell division – many times results in permanent impairment

  20. Dendrites • Soma • Axon terminals • Axon

  21. Neuron Structure • Many neurons have axons covered in a protective layer – myelin sheath – that insulates to prevent sideways transmission • Increases speed of transmission (100x) • composed mainly of lipids and is white like animal fat • Nervous tissue of myelinated cells is called white matter

  22. Neuron Structure • Gray matter are unmyelinated neurons • Transmit impulses slower

  23. Potassium channels are ‘leaky’ and allow potassium to passively move to the outside • The sodium-potassium pump in the neuron membrane moves sodium out and potassium in • Using ATP, the sodium-potassium pump moves 3 Na+ out for every 2 K+ in • This restores the potassium levels in the cell

  24. The depolarization – loss of charge difference – moves in a wave down the cell

  25. Repolarization – when potassium ions leave and internal cell state is more negative than outside

  26. Synaptic Transmission • After traveling along the axon, the signal must be passed along to the next neuron • Most neurons are not physically connected • Synapse – the gap between two neurons

  27. Communication between neurons, or muscles, or glands

  28. Animations of synaptic transmission

  29. Synaptic Transmission What would occur if the neurotransmitter stayed in the synapse? • After the neurotransmitter causes the response • Removed from synapse • Enzymes break down neurotransmitters • Reuptake – some neurotransmitters are reabsorbed by the presynaptic neuron • By enzymatically breaking down and reuptake of neurotransmitters, there is no continuous stimulation of the postsynaptic cell

  30. Neurotransmitters • Chemicals that are released from one neuron at the presynaptic nerve terminal. Neurotransmitters then cross the synapse where they may be accepted by the next neuron at a specialized site called a receptor.

  31. Norepinephrineaka: adrenalin • Released from brain and ANS • Adrenal gland • Excitatory • Sense of feeling good • Monoamine • Can be used to manage hypertension

  32. Dopamine • Released from brain (CNS) • hypothalamus • Receptors: heart, kidneys, bld vessels • Inhibitory • sense of feeling good • Parkinson’s Disease • amine

  33. Serotonin • Brain (CNS) • Regulates endocrine activity (hormonal controls) • Leads to sleepiness • Controls sleep/wake cycles • amine • Inadequate amounts: • Severe depression and obsessive/compulsive disorders, anger issues, and eating disorders

  34. Endorphins • Neuropeptide • Produced in brain (CNS) • Pain relief: inhibitory • Released in times of pain or stress • Elevated levels cause disease known as Addison’s disease • Structure is similar to??? • morphine

  35. Neurotransmission, Alzheimer’s, Depression, Parkinson’s, and ADD • Depression is a disease • Feelings of helplessness and despair and thoughts of suicide • It may involve three neurotransmitters • Serotonin & dopamine (inhibitory) and norepinephrine (excitatory)

  36. Parkinson’s disease is a malfunctioning of neurons that produce dopamine, causing nerve cells to fire without regulation • Tremors, rigidity and slowed movements

  37. Neurotransmission, Alzheimer’s, Depression, Parkinson’s, and ADD • ADD may be due to abnormal levels of dopamine • Dopamine controls emotions as well as complex movements • May be due to overabundance of dopamine receptors on presynaptic cells – too much reuptake

  38. Ritalin® • Ritalin is thought to increase dopamine’s ability to stimulate postsynaptic cells • Block reuptake receptors in presynaptic cells • Dopamine in synapse longer • Stimulants in high doses result in • Euphoric feeling • More energy and endurance • Sense of power • Feeling of mental sharpness • After the stimulants wear off, user feels • Heightened fatigue • Insomnia • Poor concentration • Irritability • Tearfulness • Depression

  39. Drugs alter chemistry in the brain….altering behavior!

  40. Label the Neuron belowmyelin, nucleus, dendrite, axon terminal, shwann cell, soma, Nodes of Ranvier 1 7 6 2 5 4 3

  41. Sensory Structures