Biological Psychology: Neurons and Cells

Is the study of the psychological, evolutionally, developmental mechanism of behaviors and experience; Seeks biological explanations of behaviors

cells that receive information and transmit it to other cells; The human brain contains approximately 100 billion individual neurons; 16 billions in Cerebral cortex, 69 billions in Cerebellum, Less than 1 billion in the rest of the brain, and 1 billion in spinal cord
- their shape is distinctive compared to other

In the late 1800s, HE was the first to demonstrate that the individual cells comprising the nervous system remained separate- they did not merge into each other

structure that separates the inside of the cell from the outside environment; selectively permeable

structure that contains the chromosomes; Cell brain

structure that performs metabolic activities; takes in nutrients, breaks them down, and creates energy rich molecules for the cell.
- have its own genes

sites for cell synthesization of new protein molecules Ritalin

network of membranous thin tubes that transport newly synthesized proteins to other locations; functions as a manufacturing and packaging system

neuron that receives excitation from other neurons and conducts impulses to a muscle; Has its soma in the spinal cord

neuron that is highly sensitive to a specific type of stimulation

structure containing the nucleus, ribosomes, and mitochondria; Responsible for the metabolic work of the neuron; Covered with synapses on its surface in many neurons

Branching fibers with a surface lined with synaptic receptors responsible for bringing information into the neuron; Some also contain dendritic spines that further branch out and increase the surface area of the dendrite; The greater the surface area of the dendrite, the more information it can receive

short outgrowths that increase the surface area available for synapses; includes of shaft and spine

thin fiber of constant diameter; the neuron's information sender; The axon conveys an impulse toward other neurons, an organ, or a muscle; Axons can be more than a meter in length; Presynaptic terminals at the end points of an axon release chemicals to communicate with other neurons; maybe have a myelin sheath

insulating material that covers vertebrate axon; contains interruptions in the sheath known as nodes of Ranvier

interruptions in the myelin sheath of vertebrate axons; At each node of Ranvier, the action potential is regenerated by a chain of positively charged ions pushed along by the previous segment.

disease in which the myelin sheath is destroyed; Associated with poor muscle coordination and sometimes visual impairments.

(end bulb or bouton) point where an axon releases chemicals

axon that brings information into a structure

neuron that carries information away from a structure

neuron whose axons and dendrites are all confined within a given structure

Neurons vary in size, shape, and function; The shape of a neuron determines it connection with other neurons and its contribution to the nervous system; The function is closely related to the shape of a neuron
- Example: Purkinje cells of the cerebellum branch extremely widely within a single plane; Bipolar neurons in the retina have only short branches, and some receive input from as few as two other cells.

type of cell in the nervous system that, in contrast to neurons, does not conduct impulses over long distances; "glue"; non-neuronal cells
; maintain homeostasis, form myelin, and provide support and protection for neurons in the CNS and PNS

star-shaped glia that synchronize the activity of the axons by wrapping around the presynaptic terminal and taking up chemicals released by the axon; If a few of associated axons are active at once, the astrocyte absorbs some of the chemicals they release and then temporarily inhibits all the axons

cells that remove waste material (dead cells and weak synapses...) and other microorganisms such as viruses and fungi from the nervous system

glia cells that build myelin sheaths (In the CNS)

(In the PNS) glia cells that build myelin sheaths SCN (Suprachiasmatic nucleus)

cells that guide the migration of neurons and the growth of axons and dendrites during embryological development

A mechanism that surrounds the brain and blocks most chemicals from entering; Because neurons in the brain generally do not regenerate, it is vitally important for the blood brain barrier to block incoming viruses, bacteria, or other harmful material from entering

Most large molecules and electrically charged molecules cannot cross from the blood to the brain; A few small, uncharged molecules such as O2 and CO2 cross easily; Active transport systems pump glucose and amino acids across the membrane

a protein-mediated process that expends energy to enable a molecule to cross a membrane; Glucose, certain hormones, amino acids, and a few vitamins e.g. iron, A, and D, are brought into the brain via active transport

The blood-brain barrier is essential to health, but can pose a difficulty in allowing chemicals such as chemotherapy for brain cancer to pass the barrier

Some viruses, e.g. reovirus, when injected directly into the bloodstream, can cross the blood-brain barrier.
- Used to reach tumors inside the brain.
- Once inside, it replicates cancer cells and activates the immune system to attack and kill all cancer cells

a simple sugar; vertebrate neurons depend almost entirely on glucose; Because metabolizing glucose requires oxygen, neurons need a steady supply of oxygen; Although neurons require glucose, glucose shortage is rarely a problem, except during starvation; A more likely problem is an inability to use glucose; the human brain constitutes 2% of the body's weight, but it uses about 20% of its oxygen and 25% of its glucose

vitamin, necessary to use glucose

Prolonged thiamine deficiency, common in chronic alcoholism, leads to death of neurons and a condition called Korsakoff's syndrome, marked by severe memory impairments.

- The electrical message that is transmitted down the axon of a neuron; Does not travel directly down the axon, but is regenerated at points along the axon so that it is not weakened
- The speed of this ranges from less than 1 meter/second to 100 meters/second
- The brain is not set up to register small differences in the time of arrival of touch messages
- However, in vision, movements must be detected as accurately as possible
- The properties of impulse conduction are well adapted to the exact needs for information transfer in the nervous system

difference in electrical charges between the inside and outside of the cell (membrane); tends to pull potassium and sodium ions into the cell

condition of a neuron's membrane when it has not been stimulated or inhibited; Inside = slightly negative (-70mv)
- refers to the state of the neuron prior to the sending of a nerve
impulse

Researchers measure the resting potential by inserting a very thin microelectrode into the cell body; The diameter of the electrode must be small enough to enter without damaging the cell. The most common electrode is a fine glass tube filled with a salt solution, tapering to a tip diameter of 0.0005 mm or less. A reference electrode outside the cell completes the circuit

Contains phosopholipid molecules and protein molecules

ability of some chemicals to pass more freely than others through a membrane; Sodium, potassium, calcium, and chloride pass through channels in the membrane

mechanism that actively transports sodium ions out of the cell while drawing in two potassium ions; 3 Na out and 2 K in;
- Helps to maintain the electrical gradient;

- When the membrane is at rest:
-Sodium channels are closed.
- Potassium channels are partially closed allowing the slow passage of potassium

difference in distribution of ions across the neuron's membrane; tends to push potassium ions out of the cell and pulls sodium ions into the cell

all-or-none message sent by an axon; Action potentials can back- propagate into the cell body and dendrites-
Dendrites become more susceptible to structural changes responsible for learning

decreasing polarization toward zero across a membrane Depression

increasing polarization across a membrane

minimum amount of membrane depolarization necessary to trigger an action potential; A rapid depolarization of the neuron will occur after reaching the threshold of excitation

principle that the amplitude and velocity of an action potential are independent of the stimulus that initiated it; - Action potentials are equal in intensity and speed within a given neuron.
- Action potentials vary from one neuron to another in terms of amplitude, velocity, and shape
- Studies of mammalian axons show that there is much variation in the types of protein channels and therefore in the characteristics of the action potentials

After an action potential occurs, sodium channels are_____

The neuron is returned to its resting state by_____

The sodium-potassium pump later_____

1. At the start, sodium ions are mostly outside the neuron, and potassium ions are mostly inside.

2. When the membrane is depolarized, sodium and potassium channels in the membrane open.

3. At the peak of the action potential, the sodium channels close.

membrane channel whose permeability to sodium (or some other ion) depends on the voltage difference across the membrane

drug that attaches to the sodium channels of the membrane, stopping action potentials (ex. Novocain and Xylocaine)

transmission of an action potential down an axon

an insulating material composed of fats and proteins

axons covered with myelin sheaths

the jumping of action potentials from node to node

time when the cell resists the production of further action potentials

a time when the membrane is unable to produce an action potential

time after the absolute refractory period that requires a stronger stimulus to initiate an action potential

Have short axons, exchange information with only close neighbors, and do not produce action potentials; When stimulated, produce graded potentials; Difficult to study due to their small size; Most of our knowledge has come from the study of large neurons

a membrane potential that varies in magnitude in proportion to the intensity of the stimulus; do not follow the all-or- none law; Depolarize or hyperpolarize in proportion
to the stimulation

Step 1 of the action potential

Step 2 of the action potential

Step 3 of the action potential

Step 4 of the action potential

Step 5 of the action potential

Step 6 of the action potential

In a motor neuron, the action potential begins at the axon hillock (a swelling where the axon exits the soma)