HBS unit 2

Why is the story of Phineas Gage considered so extraordinary? What does his story teach us about the brain?

The story of Phineas Gage is extraordinary because he was able to survive and function after a railroad spike impaled his brain. It teaches us that the brain has great plasticity.

What was the supposed rationale behind Gall's phrenology map?

That the size and shape of the skull reflects a person's mental capabilities.

How did Broca and Wernicke determine the location of key language areas in the brain?

People who struggled with language and couldn't speak were studied and they either lacked those regions in the brain or had lesions.

Describe one method scientists are currently using to map the function of the human brain.

A PET scan detects a radioactive form of glucose as it travels the brain. The PET scan can see its path.

Explain the function of the brain's limbic system.

The limbic system plays a role in memories, emotions, motivation, behavior, etc. The system is closely linked to the endocrine system via glands including the pituitary gland.

Describe two ways communication occurs within the human body.

The nervous system sends messages via electrical impulses. Ex. Your brain directs your body's movement. If this could not occur then that would likely be due to a break in the pathway in the spinal cord/vertebrae which would cause paralysis.

The endocrine system .

includes glands that secrete hormones to trigger certain things

Which system is the master nervous system?

Nervous because the brain sends signals throughout the body. Endocrine could be argued but it is directed by the brain.

Examples of loss of communication in the body.

-Alzheimer's disease makes the brain stop functioning in various regions. Though it starts in the hypothalamus (memories), it eventually prevents the brain, and therefore body, from functioning.

Paralysis

prevents the body from moving because impulses cannot direct the body to perform various movements.

Diabetes

prevents communication that would trigger insulin secretion from the pancreas.

The gyri and sulci on the brain greatly increase the brain;s surface area. How do you think the increase in surface area relates to improved brain function?

The more surface area there is, the more neurons there would be, the more synapses, meaning an overall increase in brain function.

Can you think of another organ in the human body that is shaped specifically to increase surface area? How does this organ's structure relate to its function in the body?

The digestive system in humans tend to have increased surface area because it will increase the amount of nutrients absorbed. In the small intestine, not only are there folds in the tract, but there is also villi and microvilli within the intestine which also increase surface area. This is also true in the stomach where there is a rugae that increases surface area.

How do the CNS and PNS work together to control the body?

The CNS directs the PNS by sending neural impulses down the brain stem and then spinal cord where the PNS continues to direct the impulse to the muscles that need to perform the action.

Describe the path of an electrical impulse.

An electrical impulse moves from one neuron to another and first enters the dendrites. It then passes through the axon which is protected by the fatty myelin sheath. By passing through each section of the myelin sheath it passes the nodes of ranvier. This is followed by the axon terminals. It then enters the synapse and approaches neurotransmitters.

Describe one way in which neurons are similar to other cells in the body and one way in which they are different.

Like other cells, neurons have a cell membrane, cytoplasm, nucleus, mitochondria, and other organelles. They differ because they cannot perform mitosis.

How woulda person be affected if the myelin on their neurons was damaged or destroyed?

The speed of the impulses would become slower, therefore becoming less functional.

Explain how neurons convey information using both electrical and chemical signals.

Neurons send electrical impulses that travel down the neuron and trigger the release of chemicals called neurotransmitters.

"When you learn something new, you grow new neurons." What would you say to disprove this statement?

You have the same neurons as you did as a baby; neurons do not reproduce. They do form new connections when learning something new.

How do anesthetics that reversibly bind to Na channels and block the movement of sodium ions keep you from feeling pain?

It prevents the electrical impulses from being created. If it does this to nerves responsible for relaying pain then that message cannot be delivered to the brain.

What do the terms hydrophilic and hydrophobic mean and how do they relate to the structure of a cell membrane?

Hydrophilic means attracted to water while hydrophobic means not attracted to water. They relate to the structure of a cell membrane because cell membranes are made up of a phospholipid bilayer. The hydrophilic heads face the water, while the hydrophobic tails are within the bilayer and do not interact with the water.

How does the location of these ions relate to the overall membrane potential at this point?

The charge is dependent on the distribution and quantity.

The Na/K pump pumps 3 Na ions out of the cell for every 2 K ions it brings into the cell. Is this specialized protein active or passive?

Active transport because it uses ATP to function and move the ions against the gradient.

What causes the inside of the membrane to reverse charge and begin the action potential?

K+ channels closing and Na entering the cell begins action potential.

What membrane protein is responsible for restoring the original concentration of NA and K?

Na/K pump

What happens when the action potential reaches the end of the axon at the axon terminals? How does one neuron communicate with another neuron and complete the circuit?

It enters the synapse to eventually get to another neuron. It triggers the release of neurotransmitters which are received from the adjacent neuron.

What causes the reaction time to increase?

As more factors are added to complete a task, action potential has to travel a greater distance.

Why does reaction time differ in voluntary and involuntary action?

Involuntary activation was faster because the message has to travel to the spinal cord, rather than all the way to the brain, like voluntary activation. This is because involuntary activation is a reflex.

What do you think is the evolutionary significance of reflexes?

Reflexes are key to survival because damage would be done to the body if the reaction time was any longer. By reacting faster the damage can be limited. For example, when something bright shines in our eyes we squint or close our eyes to reduce damage to the eyes. Or if we touch something hot we pull our hand back.

What are two ways that reflex reactions help maintain homeostasis in the human body?

To maintain a homeostatic body temperature the body's reflex is to sweat and cool down or to minimize surface area to warm up. The body also sneezes to get out irritants and invaders from the body to maintain health.

Explain how other body systems are affected by alzheimer's.

As alzheimer's spreads throughout the brain it moves beyond memory. Eventually it destroys parts of the brain responsible for involuntary tasks in the body. The brain 'forgets' how to breath or how to pump blood (respiratory, cardiovascular).

Explain why even when their bodies seem to be failing, people with ALS have all of their mental functions and sense intact.

ALS is the loss of motor control (motor neurons), not interneurons or sensory neurons. Therefore their mental functions remain intact but they lose function in the body.

Brain stem

The part of the brain composed of the midbrain, pons, and medulla oblongata and connecting the spinal cord with the forebrain and cerebrum.

Central nervous system

The part of the nervous system which in vertebrates consists of the brain and spinal cord, to which sensory impulses are transmitted and from which motor impulses pass out, and which supervises and coordinates the activity of the entire nervous system.

Cerebellum

A large dorsally projecting apart of the brain concerned especially with the coordination of muscles and the maintenance of bodily equilibrium, situated between the brain stem and the back of the cerebrum, and formed in humans of two lateral lobes and a median lobe.

Cerebrum

The dorsal portion, composed of right and left hemispheres, of the vertebrate forebrain; the integrating center for memory, learning, emotions, and other highly complex function of the central nervous system.

Gyrus

A convoluted ridge between anatomical grooves.

Limbic System

A group of subcortical structures of the brain that are concerned especially with emotion and motivation.

Lobe

A division of a body organ marked off by a fissure on the surface.

Peripheral Nervous System

The part of the nervous system that is outside the central nervous system and compromises the cranial nerves excepting the optic nerve, the spinal nerves, and the autonomic nervous system.

Phrenology

The study of the conformation of the skull based on the belief that it is indicative of mental faculties and character.

Sulcus

A shallow furrow on the surface of the brain separating adjacent gyri.

What is communication?

Messages passing from one entity to another and being understood by the second entity.

What are consequences of miscommunication in the body?

When there is miscommunication within our central nervous system we might misunderstand sensory input or our bodies might do things we don't want them to (uncontrolled movements, lack of balance, paralysis, mental illness, etc.)

Hippocampus

Memories

Hypothalamus

Pleasure and desire

Amygdala

Anger/rage

Frontal Lobe

Inhibits urges, allows abstract thought, extremely flexible, allows consciousness. Allows speech through Broca's area

Voluntary movement using the motor cortex

Broca's Area

Speaking

Motor Cortex

Voluntary movements

Parietal Lobe

Identifies objects and understands spatial relationships. Processes sensory info using sensory cortex

Temporal Lobe

Hearing and speech memory. Processes speech using Wernicke's area.

Occipital Lobe

Sight and visual memory and reading.

Action Potential

A momentary reversal in electrical potential across a plasma membrane that occurs when a cell has been activated by a stimulus.

Axon

A long nerve cell process that usually conducts impulses away from the cell body.

Dendrite

Any of the usually branching protoplasmic processes that conduct impulses toward the body of a neuron.

Ion

An atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons.

Myelin sheath

In a neuron, an insulating coat of cell membrane from Schwann cells that is interrupted by the nodes of Ranvier.

Neurologist

A physician skilled in the diagnosis and treatment of disease of the nervous system.

Neuron

A nerve cell; the fundamental unit of the nervous system, having structure and properties that allow it to conduct signals by taking advantage of the electrical charge across its cell membrane.

Neurotransmitter

A substance that transmits nerve impulses across a synapse.

Reaction Time

The time elapsing between the beginning of the application of a stimulus and the beginning of an organism's reaction to it.

Reflex

An automatic and often inborn response to a stimulus that involves a nerve impulse passing inward from a receptor to the spinal cord and thence outward to an effector without reaching the level of consciousness and often without passing to the brain.

Synapse

The place at which a nervous impulse passes from one neuron to another.

Neurons

Send electrical signals through body

Dendrites

Pick up signal

Axon

Carry signal long distances

Myelin Sheath

Insulates axon

Nodes of Ranvier

Allow nutrients in, waste out.

Axon Terminals

Branch to meet other neurons

Synapses

Place one neuron connects to next

Synaptic Cleft

Joint between neurons

Neurotransmitters

Chemicals that allow neurons to communicate with each other

Sensory Neuron

Pick up signals through senses

Send info from PNS to CNS

Interneuron

Connect sensory neurons to motor neurons

Found in CNS

Motor Neuron

Receive signals from CNS, causing movement to an effector

In PNS, receive info from CNS

How are electrical impulses created in the human body?

Na/K pump keeps outside of membrane + and inside - by pumping positive ions out of the membrane, priming the membrane to carry charges. During an action potential, there's a sudden reversal of charge, carrying a message down the axis.

Epilepsy

Bursts of electricity cause involuntary responses (seizures, odd smells, etc.)

Parkinson's

Cells that make dopamine die. The lack of this neurotransmitter causes problems in communication between neurons in the two brain regions that must communicate to allow smooth, controlled movements.

Huntington's

Genetic defect on chromosome 4 causes synthesis of abnormal protein-the protein disrupts function of certain nerve cells, ultimately leading to their deaths

Alzheimer's

Brain cells die. Communication breaks down, getting worse with time and eventually causing death.

Multiple Sclerosis

The immune system attacks the myelin around nerve axes in the brain, spinal cord and optic nerves, causing nerves to be unable to transmit messages due to a buildup of scar tissue.

ALS

Nerve cells waste way or die and can't send messages to the lower motor neurons. Movement becomes less and less controlled. Eventually the lung muscles cannot contract, causing death.

Hormone

A chemical secreted by an endocrine gland that signals a system to do something.

Example of short term hormone

Adrenalin

Example of long term hormone

Growth Hormone

Example of hormone excreted by multiple glands

Estrogen by ovaries and adrenal glands

Endocrine Glands

Pancreas, thymus, thyroid, pituitary gland, pineal gland, adrenal glands, ovaries, and testes.

Glands are ultimately controlled by

Pituitary gland and hypothalamus.

Insulin

Secreted by pancreas

Regulates blood sugar levels by allowing cells to take in sugar

GH (growth hormone)

Secreted by pituitary

Stimulates growth

FSH (follicle stimulating hormone)

Secrete by anterior pituitary

Stimulates maturity, including sexual maturity

Glucagon

Secreted by pancreas