Biopsych Exam 1

Biopsychology

• Seeks to understand behavior by studying the physiological processes that control it

• Also referred to as physiological psychology, or behavioral neuroscience

How to we learn about brain functioning?

• Animal models

• Human brain injuries

• Imaging of the brain

• Genetic methods

Experimental Ablation

Removing or inactivating part of the brain

Lesion studies

Experiments in part of the brain is damaged and the animals behavior is observed

• Discovers what functions are performed by different regions of the brain

Human Brain Injuries - Phineas Gage

Helped us to understand the role of the prefrontal cortex

Human Brain Injuries: H.M.

Helped us to understand the role of the hippocampus

Structural Brain Imaging

• X-Ray

• Computerized Tomography (CT)

• Magnetic Resonance Imaging (MRI)

Still photo

Functioning Brain Imaging

• Position emission tomography (PET)

• Functional MRI (fMRI)

• Mirco and macroelectrodes (EEGs)

Stimulating AND recording brain activity

Genetic Methods

• All behavior is determined by interactions between and individual’s brain and their environment

• Behavioral characteristics are often passed down

• May play a role in physiological differences

• Examples

  • Twin studies

  • Adoption studies

  • Genomic studies

Changes on perspectives of the brain

• Historical: brain is static and does not change in adulthood

• Now: neuroplasticity and neurogenesis

Neuroplasticity

The ability of brain areas to increase in organization, level of activation, and amount of connection to other areas based on use, practice, and experience

Neurogenesis

Involves the birth of totally new neurons

• Neurons can be regenerated

• New neurons appear throughout the lifespan

• Evidence in hippocampus

Central Nervous System (CNS)

• Brain and spinal cord

• Encased in bone (skull and vertebral column)

• Requires a large supply of blood and is chemically protected by the blood brain barrier

Peripheral Nervous System (PNS)

• Nerves that rely informed between the CNS and the rest of the body

• Cranial nerves, spinal nerves, and peripheral ganglia)

Neuron

Information-processing and information-transmitting element of the nervous systen

Label the neuron

Consists of dendrites, soma, axon, myelin shealth, axon terminal buttons

Soma (cell body)

• contains organelles including the nucleus

• Shape varies

• Appears as GRAY MATTER in the brain and nerves

Dendrites

• Branched, treelike structure

• Receives info transmitted from other neurons

Axons

• Long, thin, cylindrical structures

• Carries info from the soma to the terminal buttons

• The action potential is basic message

Myelin Sheath

• Fatty substance that surrounds the axons and insulates them

• Appears as white matter in the brain and nerves

• Helps a message travel faster

Terminal buttons

• Buds at the end of a branch of an axon

• Form synapses with another neuron

• Secrete chemicals called neurotransmitters

Axon Hillock

Where the action potential begins

Nucleus

Contains chromosomes and proteins

Mitochondria

Power plants; produces ATP

Membrane

Double layer of lipid (fat-like) molecules

Sensory neuron

• IN PNS

• Afferent - signals travel toward the CNS

• Receives sensory info (light, sound, touch, taste, odor, contact with objects)

Motor neuron

• In PNS

• Efferent - signal travels away from the CNS

• Control voluntary and involuntary motor behavior through contracting muscles/glands

Interneurons

• Connections

• Between sensory and motor neurons

• In CNS

Label da diagram

Sensory, motor, and interneurons

Astrocytes

• Supporting cell of the CNS

• Support and repair

• Nourishment

• “neuron glue”

• Phagocytosis

Oligodendrocytes

• Supporting cells of the CNS

• Multiple segments of myelin sheath

• Insulation and support

Microglia

• Supporting cell of the CNS

• Immune defense

• Phagocytosis

Schwann cell

• Support cell for PNS

• Support

• One segment of myelin sheath

Action Potential

Rapid changes in electrical charge across the membrane of a neuron

• Results in the release of neurotransmitters

Membrane Potential

Difference in charge (positive or negative) across the membrane of a neuron (inside or outside)

Extracellular fluid

• Fluid surrounding the neuron

• Contains ions

• Chloride (Cl-) and Sodium (Na+) are of highest concentration

Intracellular fluid

• Fluid inside the neuron

• Potassium (K+) and Organic Anions (A-) are of highest concentration

What are the two forces that give rise to the membrane potential?

1. Diffusion

2. Electrostatic pressure

Diffusion

movement of molecules from regions of high concentration to low concentration

Electrostatic pressure

Force exerted by attraction or repulsion that moves ions from place to place

• Cations are positive

• Anions are negative

• Anions repel each other; cations repel each other; anions and cations attract

Resting membrane potential

Axon at rest is negative inside the cell relative to the outside; neuron is polarized

• -70 mV more negatively charged inside the axon in comparison to the outside

Sodium-Potassium Pump

• Made of protein molecules embedded in the membrane

• 3 Na+ comes out of the neuron for every 2 K+ that is pumped in

  • Creates high concentration of sodium outside the cell and high concentration of potassium inside the cell

• Uses 40% of the neurons metabolic resources (ATP is provided by mitochondria)

• Without the pump, the resting potential would collapse, causing neurons and muscle cells to stop firing signals

Action potential

Consists of a series of changes in opening and closing of voltage gated ion channels along the axon of a neuron and the resulting redistribution of ions (and thus membrane potential)

What causes an action potential to occur?

• Signals from other cells or sensory inputs cause positive ions (like sodium) to enter the cell

• Begins when threshold of excitation is reached and the membrane potential moves closer to 0, becoming less negative

Threshold of excitation

• -55mV

• When reached, an action potential will fire and the voltage-gated ion channels open

Depolarization

The inside of the cell becomes less negative relative to the outside; moving the membrane potential closer to 0

• Voltage-gated ion channels open, allowing positively charged sodium ions in

• Triggers the rising phase of an action potential (electrical signal)

Repolarization

The cell returns its voltage back down to the negative resting state after depolarization

• Sodium channels close and voltage-gated potassium channels open, allowing positive potassium ions to leave the cell

• Resets the electrical charge inside the cell to the negative

• Returns the neuron to resting potential

Hyperpolarization

The membrane potential becomes more negative than the normal resting potential

• Potassium channels stay open a bit too long and potassium ions leave the cell

• Creates a refractory period where its harder for the cell to fire another signal

Voltage-gated ion channels

• Exist along the axon of a neuron and aid in the redistribution of ions and the membrane potential

• Are only opened by changes in the membrane potential

• 2 kinds: voltage gated sodium channel (allows sodium ions to rush into cell) and voltage gated potassium channel (allows potassium ions to rush out of the cell)

All or nothing law

• An action potential either occurs or does not occur

• Once threshold of excitation is reached, an action potential will always occur

Synaptic Transmission

Primary means of communication between neurons

Structure of synapses

Pre and postsynaptic membranes

Face each other across the synapse

Synaptic vesicles

Made of membrane and filled with molecules

Neurotransmitters

Naturally occurring chemicals (endogenous), produced and released by neurons

Postsynaptic receptors

Specialized proteins that bind neurotransmitters released from presynaptic neurons, facilitating the transmission of neural signals

Synaptic Cleft

The space between terminal buttons of one neuron and dendritic or somatic membrane of another

Release of neurotransmitter

1. Action potential reaches terminal button

2. Vesicles (filled with neurotransmitters) on the presynaptic membrane open

3. Neurotransmitter is released into the synaptic cleft

   1. Called Exocytosis

4. Molecules of neurotransmitters move from areas of high concentration to disperse across synapses (diffusion)

Exocytosis

Vesicles fuse with presynaptic membrane, open, and spill their contents into the synaptic cleft

Activation of receptors

• NTs (either excitatory or inhibitory) fit the binding sites of receptors

• This conveys the neural message from the presynaptic cell to the postsynaptic cell

• Once binding occurs, the postsynaptic receptors open neurotransmitter-dependent ion channels

• Movement of these ions changes local membrane potential (depends on what ion channel is opening)

Excitatory neurotransmitter

increase the likelihood that the neuron will fire an action potential

• depolarization

Inhibitory neurotransmitter

decrease the likelihood that a neuron will fire an action potential

• hyperpolarization

Termination of Postsynaptic potentials

Reuptake or Enzymatic deactivation

Reuptake

Extremely rapid removal of a neurotransmitter from the synaptic cleft by the terminal button

Enzymatic deactivation

Accomplished by enzyme that destroys molecules of the neurotransmitter

• Ex: Acetylcholinesterase (AChE) deactivates acetylcholine (ACh)

Discovery of the Blood Brain Barrier

• Paul Ehrlich’s experiment over 100 years ago

• Injected dye into mice (dye injected in body stayed separate from the brain and vice versa)

Blood-Brain Barrier

• Selectively permeable barrier produced by the cells in walls of brain’s capillaries

• Let’s in only what is needed and keeps out what could be harmful

  • Maintains the right ionic balance within the brain and blocks substances that would disrupt neural functions

• Some substances must be actively transported through the capillary walls by special proteins

Blood flow and the BBB

• Brain receives up to 20% of blood flow from the heart

  • 1 sec interruption = uses too much dissolved oxygen

  • 6 sec interruption = unconsciousness

  • Few minutes = permanent brain damage

Cerebrovascular Disease or Stroke

• Most common type of life-threatening injury to the brain in the U.S. and 5th most common cause of death

• Happens when a blood clot or broken vessels presents blood from getting to the brain

Meninges

• Protective sheaths around the brain and spinal cord

Dura Mater

• Outermost meninges

• Durable, thick, tough

• Unstretchable

Arachnoid Membrane

• Middle meninges

• Soft and spongy with weblike tissue

Subarachnoid Space

Fluid-filled space that cushions the brain

• Between arachnoid membrane and pia matter

• Protects from head trauma

• Reduces brain from 1400kg (3lb) to 80kg (1lb)

  • Contains cerebrospinal fluid (CSF)

Pia Matter

• Innermost meninges

• Follow every surface of the brain

Ventricular System

• Consists of a series of 4 ventricles (hollow, interconnected chambers)

• Produce and contain the cerebrospinal fluid, which provides support, nourishment, and removes waste

Cerebrum

• Largest part of the brain (accounts for 4/5 total weight)

• Divided into 2 symmetrical cerebral hemispheres

  • Made up of cerebral cortex, limbic system, and basal ganglia

Cerebral Cortex

• surrounds the cerebral hemispheres

• 4 lobes

• Consists mostly of glia, cell bodies, and dendrites

  • Grayish appearance called gray matter

• Beneath are millions of axons that connect to other areas of the brain

  • White matter

Gray matter

Glia, cell bodies, and dendrites in the cerebral cortex

White Matter

Millions of axons that connect to other areas of the brain beneath the cerebral cortex

• Large concentration of myelin gives it the opaque white color

Four Lobes of the brain (label)

1. Frontal

2. Parietal

3. Occipital

4. Temporal

Sensory cortices

Receive information from sensory organs; info sent to the contralateral hemisphere (except taste and smell)

Primary visual cortex

• Receives and processes visual info

• Located in occipital lobe

Primary auditory cortex

• Receives and processes auditory information

• Located in temporal lobe

Primary somatosensory cortex

• Receives and process somatic info (detecting touch, body position and movement in space), pain, pressure, and temp

• Located in parietal lobe

Motor cortex

• Most directly involved in control of movement

• Neurons in different parts of this are connect to muscles in different parts of the body

  • Contralateral

• Located in front of the primary somatosensory cortex in the frontal lobe

Label this diagram

Prefrontal Cortex

Involved in executive functions (i.e. formulating plans, setting goals, regulating emotions)

Limbic System

• Subcortical nuclei

• Involved in survival behaviors and emotional responses

• Includes hippocampus, amygdala, and cingulate gyrus

Hippocampus

Learning and memory

Amygdala

Processing center for emotions

Cingulate gyrus

Processing emotions, behavior regulation, regulating autonomic motor function

Basal Ganglia

• Group of subcortical nuclei

• Involved in the control of movement, attention, and reward processing

  • Proper functioning requires dopamine

  • Involved in parkinson’s, SUDs, and ADHD

Thalamus

• Relay for motor and sensory signals to the cerebral cortex

Hypothalamus

• Controls autonomic nervous system and endocrine systems (fight, flight response)

• Produces and controls secretion of hormones in conjunction with the pituitary gland

• Organizes behavior related to the survival of the species

Cerebellum

• Receives auditory, visual, vestibular, and somatosensory info and info about individual muscle movements

• Integrates info and modifies the motor outflow; coordinates and smooths movements

• Alcohol impairs functioning

Pons

• Large bulb in brainstem

• Sleep and arousal

• Relays info from the cerebral cortex to the cerebellum

Medulla

Controls vital functions such as regulation of the cardiovascular system, respiration, and skeletal muscle tone

Somatic Nervous System

• Involved in conscious activities

• Spreads outward from brain and spinal cord

• Receives sensory info from sensory organs and controls movements of skeletal muscles through cranial and spinal nerves

Spinal Nerves

• 31 pairs that begin at the junction of the nerve roots of the spinal cord

• Nerves leave the vertebral column and travel to the muscles or sensory receptors branching repeatedly as they go

  • Efferent (motor) and afferent (sensory)

Cranial Nerves

• 12 pairs are attached to the ventral surface of the brain

• Efferent (motor) and afferent (sensory)