HBS Unit 2

Cerebrum

Gray matter of the brain composed of 4 lobes

Frontal lobe

Reasoning, problem solving, speech production (Brocas area), movement (motor cortex)

Parietal lobe

Sensory info (sensory cortex), touch sensation

Temporal lobe

Language understanding (wernickes area), hearing

Occipital

Vision

Cerebellum

Balance, muscle coordination

Brain stem

composed of midbrain, pons, and medulla oblongata

Blood pressure, sleeping and waking

Medulla oblongata

Breathing

Corpus Callosum

Rough part of the brain that Ensures both hemispheres can communicate

processes sensory, motor, and cognitive signals

Gyri

Elevated ridges

Sulci

Valleys/fissures

Cranial nerve I

sense of smell

Cranial nerve II

info on sight

Cranial nerve III

relays info for eye movement

Cranial nerve IV

ability to look down at your nose

Cranial nerve V

face sensation and chewing

Cranial nerve VI

ablity to move eyes away from nose

Cranial nerve VII

facial expression (bels palsy)

Cranial nerve VIII

hearing info and balance

Cranial nerve IX

oral sensation, taste, salivation

Cranial nerve X

longest nerve, heart rate, blood pressure

Cranial nerve XI

shoulder elevation and head turning

Cranial nerve XII

tongue movement

Radial nerve

works with triceps for arm extension

Ulnar nerve

innervates flexors of forearm

Brachial plexus

connects spinal cord to arm and hands

innervates muscles of upper and forearm

Spinal nerves

carry information to and away from the spinal cord

innervates skin and back muscles

Median nerve

movement for forearm, wrist, and hand

innervates lateral aspect of palm

Sciatic nerve

movement/sensation in legs and feet

posterior leg muscles and bottom of foot

Flexor Retinaculum

stabilize carpal system

Henry Molaison

• had his hippocampus and amygdala removed for seizures

• Couldn’t form new memories

• Showed links between median temporal lobe portions and memory problems

• Linked conscious and unconscious memory

Phineas Gage

• rod through head, damaging front, left brain

• Link between personality change and brain injury

Brocas Area

• man came in only able to produce a single syllable

• Found a tumor in an area of the left frontal lobe of those suffering from speech difficulties

• Lower frontal lobe → responsible for speech production

Glial cells

provide protection and maintain homeostasis for neurons, damage can cause brain tumors

Ependymal

CNS: metabolism of neuron, in Cerebrospinal fluid

Oligodendrocytes

CNS: produce myelin sheaths, can work with multiple sheath sections

Astrocytes

CNS: clean excess neurotransmitters

Microglia

CNS: Protection/defense

Schwann cells

PNS: In individual sheath sections, essential role in development,maintenance, regeneration of peripheral nerves, produce sheath

Satellite cells

PNS: muscle regeneration

Afferent

Conducting towards brain

Efferent

Conducting away from brain

Multipolar

Contain one axon and one or 2 dendrites from cell body, CNS and efferent PNS, most abundant

Bipolar

2 processes extending from either side of cell body (one dendrite and one axon), in the retina

Pseudounipolar

One process from cell body that splits into 2 axons (one for PNS one for CNS), only in sensory organs

Unipolar

Have a single process extending from cell body, most common in invertebrates, afferant PNS

Motor neuron

Multipolar, PNS, transmits signals to muscles, efferent, short dendrites, long axon

Sensory neuron

PNS, external signals to CNS, mostly pseudounipolar (can be bi or unipolar), afferent, short axons, long dendrites

Interneuron

CNS, association neurons, Most abundant, regulates neuron activity, multipolar, no myelin sheath

How do ions move?

From high to low concentration

What are the starting charges of the cell?

Interior: - Exterior: +

Depolarization

• When a signal is received and the membrane has reached its threshold, sodium channels open and let in sodium.

• This reverses the charges of the interior and exterior of the cell,causing the action potential.

Repolarization

Cell returns to resting potential when the potassium pump opens letting out potassium

Hyperpolarization

The cell overshoots the amount of potassium needed to be let out, resulting in the membrane potential dropping lower than resting state.

Sodium-potassium pump

• Use ATP

• 3 sodium out for every 2 potassium in

• Maintains high sodium extracellularly and high potassium intracellularly

Steps of signal transfer

• When a nerve impulse arrives at the terminal it causes calcium ions to move into the cell

• The vesicles fuse with the membrane and release neurotransmitters into the synaptic cleft

• The neurotransmitters bind to receptors on the receiving neuron

• The binding activates ion channels and caused the steps of action potential

ACH

muscle contraction, learning, and memory

Dopamine

pleasure, motivation, mood, attention, memory, and movement

GABA

CNS, primary inhibitory neurotransmitter. signal regulation, normal brain function

Glutamate

primary excitatory neurotransmitter

Epinepherine and norepinepherine

excitatory, fight or flight, increases arousal/attention

Serotonin

regulation of mood and sleep, aids in digestion

Agonist

mimics the effects of a neurotransmitter (morphine)

Antagonist

 a drug that binds to a receptor but doesn’t activate it (blocks or reduces another drug) caffeine

Inverse agonist

binds to the same receptor of the agonist but produces an opposite effect (diphenhydramine)

Reuptake Inhibitor

stops or delays the absorbtion of neurotransmitters (cocaine)

Reward pathway

governs motivated behavior (pleasure and euphoria)

• hippocampus

• amygdala

• midbrain

• prefrontal cortex

Explain opioid addiction

• Opioids mimic the effects of dopamine

• The body associates opioids with these feelings of pleasure and euphoria, causing a craving

• The body also stops producing dopamine on its own, since it gets it artificially

• Reduction of dopamine causes drug tolerance

Model organism

an organism that stands as a substitute for a human

Reflex

automatic, doesn’t reach consciousness/brain

Reaction

Voluntary, requires more processing

Reflex arc

• Patellar reflex is initiated by tap on patellar tendon

• Tap causes slight stretching of quads activating stretch receptor

• Begins a nerve impulse that travels to the spinal cord

• Motor neurons activate even without signal reaching the brain

• Motor neurons bring signal back to muscles, causing contraction

Signal speed

• Multiply distance measured from spinal cord to tendon by 2 (account for trip to and back)

• Divide the total distance by mean time

• Convert to meters per second from cm

How many neurons does the brain have

86 billion

How thick is synapse compared to paper

synapse: 20-40nm

Paper: 100,000nm

How do you find signal speed?

• multiply the distance from the spinal cord to tendon by 2

• Divide the total distance by the mean time (of reaction times)

• Convert to meters per second

Development of nervous system

Babies

• born with lots of instinctual reflexes that fade away

• Slow reaction time and low concentration

Toddlers

• build better coordination and cognitive function

Teens/young adults

• refining cognitive skills and coordination

• Better focus and faster reactions

• Reaction time peaks at 24

Middle age

• brain functions begin to decline

• White matter in brain decreases

• Reduction of synapses

Senior

• brain shrinks

• Neurons shrink, retract dendrites, and myelin deteriorates

• Neuron communication is less effective

Pineal gland

Regulates sleep cycle, secrete melatonin

Hypothalamus

Reproduction, thyroid regulation, growth, emotions, water levels, stress response

Pituitary gland

Growth, metabolism, reproduction, lactation, water balance, childbirth, stress/trauma

Thyroid gland

Metabolism, growth/development

Thymus

Makes up leukocytes until puberty, releases hormones to control the pituitary gland

Adrenal gland

Stress response, metabolism, blood pressure, immune system

Pancreas

Blood sugar, appetite, stomach acid, controls when to empty stomach and releases amylase, protease, and lipase

Ovaries

Estrogen and progesterone, reproduction and menstruation

Testis

Sperm and testosterone, muscle development, body hair, voice deepening

Type 1 diabetes

Pancreas make little to no insulin, usually in children

Type 2 diabetes

Insulin receptors stop working

Testosterone

Builds bone, muscle mass, body hair, development of reproductive tissue

• made by ovaries and testis

Estrogen

Puberty, menstruation, pregnancy, menopause, sperm development, bone health

• ovaries, testis, adrenal glands, and fat cells

Progesterone

Menstruation, pregnancy , and testosterone production

• ovaries, testis, and adrenal glands

Endocrine disrupters

BPA: makes some plastics

Phytoestrogens: naturally in some plants (sesame seeds, flax seeds, tofu, soy milk)

Phthalates: makes plastics more flexible

Triclosan: antimicrobial in soaps, toothpastes, clothing, and toys