Module 3: BIologyr

Glial cells and neurons

Glial cells and neurons

Two types of cells in nervous system

 Glial cells 

 provide scaffolding on which the nervous system is built, help neurons line up closely with each other to allow neuronal communication, provide insulation to neurons, transport nutrients and waste products, and mediate immune responses.

Neurons

serve as interconnected information processors that are essential for all of the tasks of the nervous system.

semipermeable membrane

This membrane allows smaller molecules and molecules without an electrical charge to pass through it, while stopping larger or highly charged molecules. A neuron’s outer surface

soma, or cell body.

The nucleus of the neuron is located in the

dendrites

the soma has branching extensions known as these. serve as input sites where signals are received from other neurons.

axon

signals are transmitted electrically across the soma and down a major extension from the soma known as the

multiple terminal buttons

The axon ends at:

synaptic vesicles

The terminal buttons contain

neurotransmitters, the chemical messengers of the nervous system.

synaptic vesicles house:

myelin sheath

Fatty substance which coats the axon and acts as an insulator, increasing the speed at which the signal travels.

Nodes of Ranvier

These gaps in the myelin sheath are known as the

synaptic cleft

where synaptic vesicles release neurotransmitters into the very small space between two neurons and is an important site where communication between neurons occurs.

Receptors

 proteins on the cell surface where neurotransmitters attach, vary in shape, with different shapes “matching” different neurotransmitters.

The neurotransmitter and the receptor have what is referred to as a lock-and-key relationship—specific neurotransmitters fit specific receptors similar to how a key fits a lock. The neurotransmitter binds to any receptor that it fits.

How does a neurotransmitter “know” which receptor to bind to?

resting potential. 

Between signals, the neuron membrane’s potential is held in a state of readiness, called the

membrane potential

This difference in charge across the membrane, called the

This difference in charge, known as the electrochemical gradient

provides an additional force on sodium, causing it to move into the cell.

threshold of excitation

If that charge reaches a certain level the neuron becomes active and the action potential begins.

 action potential

the electrical signal that typically moves from the cell body down the axon to the axon terminals

all-or-none phenomenon

n simple terms, this means that an incoming signal from another neuron is either sufficient or insufficient to reach the threshold of excitation. There is no in-between, and there is no turning off an action potential once it starts.

reuptake.

involves the neurotransmitter being pumped back into the neuron that released it, in order to clear the synapse

degradation 

typically involves an enzyme breaking the neurotransmitter down into it’s components, so that it can no longer interact with the receptors on the postsynaptic neuron.

biological perspective

focus on the physiological causes of behaviour assert that psychological disorders like depression and schizophrenia are associated with imbalances in one or more neurotransmitter systems

Psychotropic medications

drugs that treat psychiatric symptoms by restoring neurotransmitter balance.

Agonists 

chemicals that mimic a neurotransmitter at the receptor site.

antagonist

blocks or impedes the normal activity of a neurotransmitter at the receptor.

 somatic nervous system

associated with activities traditionally thought of as conscious or voluntary and it consists of motor neurons and sensory neurons

interneuron

located primarily within the CNS and is responsible for communicating among the neurons. allow the brain to combine the multiple sources of available information to create a coherent picture of the sensory information being conveyed.

autonomic nervous system 

controls our internal organs and glands and is generally considered to be outside the realm of voluntary control.

sympathetic nervous system

nervous system nvolved in preparing the body for stress-related activities

parasympathetic nervous system

nervous system associated with returning the body to routine, day-to-day operations.

Homeostasis 

a state of equilibrium, or balance, in which biological conditions (such as body temperature) are maintained at optimal levels.

The top of the spinal cord is a bundle of nerves that merges with the brain stem

where the basic processes of life are controlled, such as breathing and digestion

fewer

Therefore, the lower on the spine damage occurs, the ______functions an injured individual will lose.

hindbrain

located at the back of the head and looks like an extension of the spinal cord. It contains the medulla, pons, and cerebellum

medulla, pons, and cerebellum

hindbrain includes [3]

medulla 

controls the automatic processes of the autonomic nervous system, such as breathing, blood pressure, and heart rate.

pons 

serves to connect the hindbrain to the rest of the brain. It also is involved in regulating brain activity during sleep.

cerebellum 

eceives messages from muscles, tendons, joints, and structures in our ear to control balance, coordination, movement, and fine motor skills. is also thought to be an important area for processing some types of memories.

midbrain 

is comprised of structures located deep within the brain, between the forebrain and the hindbrain.

 reticular formation

centred in the midbrain, but it actually extends up into the forebrain and down into the hindbrain. is important in regulating the sleep/wake cycle, arousal, alertness, and motor activity.

substantia nigra and ventral tegmental area

. Both regions contain cell bodies that produce the neurotransmitter dopamine, and both are critical for movement. degeneration is involved in Parkinson’s. these structures are involved in mood, reward, and addiction

cerebral cortex,

The surface of the brain. is associated with higher level processes such as consciousness, thought, emotion, reasoning, language, and memory

gyri 

brain bumps/ folds

sulci

brain grooves

longitudinal fissure

deep groove that separates the brain into two halves

forebrain (largest part of the brain)

The two hemispheres of the cerebral cortex are part of the

frontal lobe

located in the forward part of the brain, extending back to a fissure known as the central sulcus. is involved in reasoning, motor control, emotion, and language.

motor cortex,

prefrontal cortex,

Broca’s area,

cortexes in fronal lobe

prefrontal cortex,

cortex which is responsible for higher-level cognitive functioning;

motor cortex,

cortex which is involved in planning and coordinating movement

Broca’s area

cortex which is essential for language production.

parietal lobe

located immediately behind the frontal lobe, and is involved in processing information from the body’s senses.

somatosensory cortex

Cortex in parietal lobe

somatosensory cortex

cortex which is essential for processing sensory information from across the body, such as touch, temperature, and pain.

temporal lobe 

lobe is associated with hearing, memory, emotion, and some aspects of language.

auditory cortex,

Wernicke’s area,

Cortexes in temporal lobe

auditory cortex

he main area responsible for processing auditory information

Wernicke’s area,

area is important for speech comprehension

occipital lobe

located at the very back of the brain, and contains the primary visual cortex, which is responsible for interpreting incoming visual information.

thalamus 

sensory relay for the brain.All of our senses, with the exception of smell, are routed through here

limbic system

is involved in processing both emotion and memory.

hippocampus, the amygdala, and the hypothalamus

he limbic system is made up of a number of different structures, but three of the most important are the

hippocampus 

an essential structure for learning and memory

amygdala 

involved in our experience of emotion and in tying emotional meaning to our memories

hypothalamus 

regulates a number of homeostatic processes, including the regulation of body temperature, appetite, and blood pressure. also serves as an interface between the nervous system and the endocrine system and in the regulation of sexual motivation and behaviour.

lateralization

pecialization of function n each hemisphere, mainly regarding differences in language functions

corpus callosum

The two hemispheres are connected by a thick band of neural fibres known as. allows for information being processed on one side of the brain to be shared with the other side.

neuroplasticity

ow the nervous system can change and adapt. can occur in a variety of ways including personal experiences, developmental processes, or in response to some sort of damage or injury that has occurred.

creation of new synapses, pruning of synapses that are no longer used, changes in glial cells, and even the birth of new neurones

Neuroplasticity involves what?

A computerized tomography (CT) scan

involves taking a number of x-rays of a particular section of a person’s body or brain. . The x-rays pass through tissues of different densities at different rates, allowing a computer to construct an overall image of the area of the body being scanned.

Positron emission tomography (PET) scan, has been replaced by he fMRI as an alternative diagnostic tool.

scans create pictures of the living, active brain. As a brain area becomes more active, more blood flows to that area. A computer monitors the movement of the tracer and creates a rough map of active and inactive areas of the brain during a given behaviour.

magnetic resonance imaging (MRI)

a person is placed inside a machine that generates a strong magnetic field. When the magnetic field is turned off, the hydrogen atoms emit electromagnetic signals as they return to their original positions.

Functional magnetic resonance imaging (fMRI)

it shows changes in brain activity over time by tracking blood flow and oxygen levels. MRI that shows changes in metabolic activity over time

With their high level of detail, MRI and fMRI are often used to compare the brains of healthy individuals to the brains of individuals diagnosed with psychological disorders. This comparison helps determine what structural and functional differences exist between these populations.

When are MRI and fMRI used

Electroencephalography (EEG)

serves this purpose by providing a measure of a brain’s electrical activity.. The signals received by the electrodes result in a printout of the electrical activity of his or her brain, or brainwaves, showing both the frequency (number of waves per second) and amplitude (height) of the recorded brainwaves,

pituitary gland

secretes a number of key hormones, which regulate fluid levels in the body, and a number of messenger hormones, which direct the activity of other glands in the endocrine system