Biological Bases of Behavior

The Nervous & Endocrine Systems

Nervous system - all nerve cells and electrochemical communications

• Central nervous system (CNS) - brain and spinal cord
• Peripheral nervous system - connects CNS to the rest of the body
• Types of Neurons:
  • Sensory/afferent - carries signals from the body’s sensory receptors to the brain
  • Motor/efferent - carries signals from the brain to the body
  • Interneurons - within the brain they process info

Peripheral Divisions:

• Somatic - enables control of skeletal muscles
• Autonomic (ANS) - controls functions like gland activity, digestion, heartbeat, etc
  • usually not consciously aware of it
• Sympathetic - amps you up in response to a stressor
  • eg. raises heart rate, blood pressure, sugar, etc
• Parasympathetic - calms you down when a stressor is over

Neural Network - groups of neurons that are near each other. work together as we learn and reinforce tasks/skills

• when learning a new skill you’re forming new brain networks

Spinal Cord reflex arc: sensory info enters the body → spinal cord intercepts signal and reacts → motor neurons receive commands from spinal cord → pain stimulants enter the brain

The Endocrine System - a set of glands that secrete hormones into the bloodstream

• Hormones - chemical messengers that act on body tissues
• Adrenal glands - near the kidneys, release (nor)epinephrine that gives us fight or flight response; feel effects for a while after event
• Pituitary gland - releases hormones related to growth but tells the other glands to release sex and stress hormones

Studying the Brain

The tools of discovery:

• lesion - tissue destruction
  • naturally or experimentally caused by the destruction of brain tissue
• (EGG) electroencephalogram - an amplified recording of the waves of electrical activity sweeping across the brain’s surface
  • the waves are measured by electrodes placed on the scalp
• CT scan - a series of x-ray photos taken from different angles and combined by a computer into a composite representation of a slice of the brain’s structure (aka CAT scan)
• PET scan - a visual display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task
• MRI - a technique that uses magnetic fields and radio waves to produce a computer-generated image of the soft tissue
• fMRI - a technique for revealing blood flow and brain activity by comparing successive MRI scans

Neurotransmitters

Acetylcholine (ACh) - involved in all body movements, slows heart rate, contracts smooth muscles

• Excess: muscle weakness, cramps, paralysis
• Shortage: dementia, Alzheimer’s

Dopamine - a feel-good hormone, gives pleasure feeling (nostalgia)

• Excess: ADHD
• Shortage: Parkinsons

Serotonin (5HT) - mood & sleep, produces melatonin; carries messages from nerve cells to brain; influence digestion, nausea, etc

• Excess: severe serotonin syndrome
• Shortage: depression, anxiety

Norepinephrine - increases alertness, constricts blood vessels, affects the sleep-wake cycle

• Excess: pheochromocytoma
• Shortage: ADHD

GABA - primary inhibitory, blocks impulses for nerve cells

• Excess: hypersomnia
• Shortage: epilepsy, autism, schizophrenia

Glutamate - learning and memory, the energy source for brain cells

• Excess: death, Parkinsons, Alzheimers
• Shortage: insomnia, concentration problems, mental exhaustion

The Cerebral Cortex

Cerebral Cortex - the intricate fabric of interconnected neural cells covering the cerebral hemisphere; the body’s ultimate control and information processing center

Structure of the Cortex:

• glial cells - cells in the nervous system that support, nourish, and protect neurons; they also play a role in learning and thinking
• 4 lobes:
  • Frontal- involved in speaking, muscle movement, thinking, planning, making judgments, and inhibiting behavior
  • location: behind the forehead
  • Parietal - involved in the processing of physical touch, helps give us our sense of body positions, helps facilitate language
  • Location: top rear of the skull
  • Occipital - involved in visual processing
  • location: far back of the skull
  • Temporal - responsible for processing hearing, involved in facial recognition
  • location: right inside and above the ears

Functions for the Cortex:

• motor cortex - an area at the rear of the frontal lobes that controls voluntary movements
• somatosensory cortex - area at the front of the parietal loves that registers and processes body touch and movement sensations
• association areas - areas of the cerebral cortex that are not involved in primary motor sensory functions; rather, they are involved in higher mental functions such as learning, remembering, thinking, and speaking

The Brain’s Plasticity:

• plasticity - the brain’s ability to change, especially during childhood, by reorganizing after damage or by building new pathways based on experience
• 2 hard facts about the effects of brain damage:
  • severed neurons usually don’t regenerate (paralysis)
  • some brain functions seem preassigned to specific areas
• neurogenesis - the formation of new neurons

Other Parts of the Brain

Medulla - the base of the brainstem; controls heartbeat and breathing

• location: where the spinal cord enters the brain

Pons - damage here can cause a coma

• location: above the medulla

Reticular formation - a relay network where neurons cross and are responsible for arousal (attention)

• location: stretches from the spinal cord through the brainstem and thalamus

Thalamus - sends signals to other parts of the brain; doesn’t have an actual function other than that

• location: atop the brainstem in the core of the brain

Hypothalamus - contains pleasure centers (releases dopamine), responsible for 4 F's: fighting, fleeing, feeding, and mating

• location: below the thalamus

Cerebellum - processes sensory inputs, enables motor coordination and associated with non-verbal learning, sense of balance

• Location: rear of the skull behind the brainstem, below occipital lobe

Amygdala - associated with emotion and aggression

• location: in the core

Hippocampus - processes conscious memories, translates immediate experiences, and transfers them to long-term memory

• location: near thalamus

Corpus callosum - connects the hemispheres and transfers messages between them

Motor cortex - controls voluntary "big" movements

• location: rear of frontal lobes

Somatosensory cortex - processes sensory inputs (especially touch)

• location: front of parietal lobes

Association areas - involved in cognitive tasks, learning, memory, reasoning, speaking, etc

• Location: all over the cerebral cortex

Broca’s Area -  responsible for language production (written, spoken, signed)

• Location: near the rear of the left frontal lobe

Wernicke’s Area - responsible for language comprehension

• Location: in left temporal lobe

  

Agonists & Antagonists

Agonists - chemicals that bind to NT receptor sites and activate a response

• full agonists - activate receptor sites at full efficiency (eg. morphine)
• partial agonists - only activate receptor sites at partial efficiency (eg. buprenorphine)

Antagonists - chemicals that bind to NT sites and block a response

• they have to be similar enough to NTs to fit in the receptor, but not so similar as to cause a response

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