Psychobiology

Psychobiology

Prof. Ismail Youssef

Every think should be made as simple as possible, but not simpler

Einstein

Study the role of physiology in the regulation and execution of behavior

THE BRAIN-Look like a lump of porridge-Consistency of blancmange-About 1.4 Kgm-It contain 10-100 billion of nerve cell-Same no. of supporting cell

•-Nerve cells differ as regards

•*Shape

•*Size

•*Kind of chemical they produced

•-Nerve cells are organized in clusters that communicate with each other and connected to other circuits

•DORSAL (Superior)

•Caudal Rostral•)Posterior) (Anterior(

•VENTRAL(Inferior)

•Central Nervous System (CNS)

• - Brain•- Spinal cord

•Peripheral nervous system(PNS)•The nerves which are attached to the

spinal cord and the base of the brain

•Brain:-Cerebral Hemispheres

•- Cerebellum

•- Brain Stem

•CNS is encased in the skull&vertebrae

•Enclosed by a three membranes called meninges ( pleural of meninx )

•They float in a fluid called Cerebro Spinal Fluid ( C S F )

•The surface of C H covered by C C •)cortex = rind ,( 3 mm ( grey matter )

•In this structure: •- Perception take place• - Memories are stored

• - Plans are formulated & executed • The nerve cells in CC are connected to other parts of

the brain by a layer of nerve fibers called ( white matter )

•

The human CC is wrinkled full of bulges (gyri ), gyrus , and grooves ( sulci ), sulcus

The large sulcus is called fissure

(We have 2 lateral and central fissures(

•Brain stem: Primitive region in Amphibion, it controls automatic behaviors such as (swallowing and breathing)

•Cerebral hemisphere: largest and most recently developed part of human brain

•Cerebellum: attached to the back of brain stem, looks like miniature version of C.H., its primary function is to control and coordinate movement.

•Peripheral nervous system PNS

•Connect CNS with: sense organs

• muscles

• glands

•-some are attached to the spinal cord.

•-others are attached directly to the brain (cranial nerve)

•Other cells (Glial cells) (G glue)

-Mechanical support

-Protection

-Guide development

-manufacturing chemicals

-Brain’s immune system

4 principle parts of neuron1-Somma: cell body , largest part of neuron2-Dentrites (Dentron G tree) receive messages and transmit the information

to the soma3-nerve fiber (axon) carries messages away from the soma towards

the cell with which the neuron communicate (the firing of an axon)

“brief changes in the electric charge of the axon”

4-the terminal button: located at the ends of the branches of the axon, terminal button secrete a chemical called a transmitter substance whenever the (fire) of the axon travel down (neurotransmitter)

Most drugs affect the chemical transmission of messages between cells.

MyelinationAxon esp. long ones are insulated with substance

called myelin (protein and fat) produced by special cells wrap themselves around the axon.

Myelin sheath is important in immunological diseases, in which the broken of myelin sheath is attacked.

-Patches of hardened, damaged tissue (multiple sclerosis)

Maturation of CNS occurs when myelination is completed

Action potential (firing)

-It is not like electricity travel through a wire

-axon transmits information at a rate less than 100 meters /second

+70 mV

-ve

_____________

-Opening of Na channel to go in, after a brief time opening of Na channel to go out (rest position)

• Synapsis• Neurons communicate with other neurons by

means of synapses.• Synapse in the conjunction of a terminal button

of one neuron and the membrane of another dendrites of neuron, muscle or gland cell

• Terminal button belong to the presynaptic neuron( the neuron that sends the messages)

• The neuron that receives the message detects the transmitter substance) is called the postsynaptic neuron

•Excitation & Inhibition•2 TYPES

•-Excitatory Post Synaptic Potential(EPSP)• Increase the likely of postsynaptic to fire•-Inhibitory Post Synaptic Potential(IPSP)

Synaptic cleft-fluid filled space-between the terminal button and the membrane of the post synaptic neuron (receptor molecule,protein)lead to opening ion channel

•EX.&IN.synapses permit ions to enter or to leave the neuron

•EX.&IN. produced by a synapse is short-lived, the effect is terminated by reuptake process

•The rate of reuptake determine how prolonged the effects of the chemical on the postsynaptic neuron will be.

•Simple neuron circuit:

•The interconnections of neurons provide us with the capacities for:

•-Perception

•-Decision making

•-Memory

•-and action

•Simple withdrawal reflex:• which is triggered by a noxious stimulus such

as contact with a hot object.• It require 3 types of neuron

•1(Sensory neuron, detect and convey the information to the spinal cord

•2(Interneuron, located in brain or spinal cord•3(Motor neuron that cause the appropriate

muscle to contract• Inhibitory neuron from the brain may prevent

this action(circuits) e.g. hot casserole

•Neuro- modulator (action at a distance) •Neurotransmitter travels a very short distance,

and affect receptor molecule located on a small patch of the post synaptic membrane

• But, some neurons release chemical that get into the general circulation of the brain and stimulate receptors on many thousands of neurons, some located a considerable distance away, They are called neuromodulator e.g. opioid

•Techniques in psychobiology•Until recently, our knowledge of the

functions of CNS was obtained through research using laboratory animals/

•1 -Lesioning:• The eldest and the common

method,correlatinga behavioral deficit with a specific damage either present or produced

•2 (Non-invasive recording of electric activity:

• a-E.E.G., The activity is seen in the form of line-tracing, Some modern machines converts the EEG data into brain map i.e. colors

•Alert: High frequency, low amplitude(12hz)

•Relax:Alpha(8-12),Theta(4-8),Delta(>4HZ)

•Event Related Potential (ERP)• Evoked Potential(EP)

•To detect the activity produced by the perception of external stimulus or the response to internal stimulus (decision making), We have the average of EP

•N100 P300•N=negative P=positive

•It appears after100 or300 millisecond of the onset of a stimulus

•3(Neuroimaging techniques• -C T computerized Tomography (Tomos means cut)

•Narrow beam x rays through a person's head computer calculates the amount of radiation that passes through it at various point

•-PET (Positron Emission Tomography)•It measures the brain metabolism, glucose consumption(

radioactive glucose)•It measures brain activity by examining the amount of

glucose consumed.•The radioactive part of glucose emit positrons “positron

emission” which are detected by a PET scanner

•MRI (Magnetic Resonance Imaging)•More details than CT

•Magnetic field is passed over the head•Reverberation are produced by hydrogen molecule and

picked up by a scanner•fMRI:using fMRI to measure the state of being in love

•-Activity was significantly high in the insula (a part of the brain involved in the visual interpretation of emotional information) and in the caudate nucleus and putamen nucleus

-Deactivation was seen in the right prefrontal parietal and middle temporal cortices.

Control of internal functions and automatic behavior

Beside CC there are other structure:-the interior of cerebral hemisphere-cerebellum-brain stemThey are important in the regulation of behavior.Cerebellum helps CH to control movement and to

initiate some automatic movements such as postural adjustment.

Interior of CH and brain stem are involved in:I Homeostasis: Homeo=similar stasis=standstill (maintain a a proper balance of physiological

variable)II Species-typical behavior: automatic behavior

exhibit by most members of species that are important to survival such as eating, drinking, fighting, courting, mating and caring for offspring.

Brain stem: contains 3 structures:

I Medulla: contains circuits of neuron that control heart rate, blood pressure and respiration rate and crawling or swimming motion esp. in simpler animals.

II Pons: circuits of neurons control sleep stages.

III Midbrain: control movements used in fighting and sexual behavior and decrease sensitivity to pain while engaged in these activities.

Endocrine gland: endo=within Krinein= to secrete-it produces hormones-it is similar to transmitter substance or neurotransmitter

except that they act over much larger distance-it produces its effect by stimulating receptors molecules

which are located on (or in) particular cells-it causes physiological reactions in these cells (target

cells)(Almost every cell of the body contain hormone receptor if

one kind or another)e.g. 6 hormones have an effect upon many neurons

Pituitary gland is the master gland, because it controls the activity of other endocrine glands

-Thyroid: control metabolism-Parathyroid: control of mineral balance-Pancreas: control carbohydrate metabolism-Adrenal Medulla: (adrenaline and

noradrenalin)_Breakdown of energy store |_Blood pressure-Adrenal cortex: (cortical steroid h) stress h.-Ovaries: estrogen control menstruation,

progesterone control pregnancy. -Testosterone: control sperm production

Hypothalamus also control automatic nervous system, the homeostatic function can be involved in either internal physiological changes or behavior through CC. Stimulation of hypothalamus lead to rage, fear and avoidance reaction

•Neural basis of instinctual behavior and emotions (The limbic system)

•-It has a role in olfaction•-Along with hypothalamus it is concerned with autonomic responses

•-It is also concerned with sexual behavior•-and concerned with the emotions of:

•* Rage- fighting and attack behavior•* Fear and avoiding reaction

•* Motivation•It was termed Rhinencephalon (smell brain)

•Were thought to be involved primarily in the sense of smell•-Around the edge of CH where they join with the brainstem

•) LIMBUS MEAN BORDER(

•Important parts are:- Amygdale-HippocampusAmygdala: emotional behavior esp. negative emotions and

it helps in providing energy for short term if prolonged stress related illness

In animals: without the amygdada it can not survive in the wild. It can not compete for food. It is considered with the encoding of memories that evoke fear “snake and monkey”

In humans: anxiety is associated with a bilateral increase in blood flow to discrete portion of the anterior end of each temporal lope.

Hippocampus: plays an important role in memory and it is also responsible for the animal reaction to the environment esp. the novel stimuli.

Rage # placidity

Normally there is a balance between Rage and placidity

Destruction of hypothalamus Rage

Destruction of Amygdala Placidity

Brain chemistry

Aminergic systems

Serotonin, Noradrenalin, Adrenaline, histamine, and Dopamine

*Serotonin

Serotonin containing neurons have their cell bodies with the midline raphe nuclei of the brain stem and project to

-hypothalamus

-limbic system

-neocortex

-spinal cord

-LSD: is serotonin agonist, first ecstasy,then depression and insomnia -plays role in sleep In animals, if we give a drug that prevents

manufacture of serotonin, it leads to prolonged wakefulness, but in human being no effect

-prolactin secretion-pain pathways-circadian rhythm-plays a role in migraine-depression??-aggressive behavior

*NorepinephrineThe cell body contain norepinephrine is located in

locus ceruleus in the pons and medulla, descend to spinal cord and cerebellum, ascend to thalamus, hypothalamus, striatum and neocortex

Drugs that increase extra cellular norepinephrine elevate mood

Drugs that decrease extra cellular norepinephrine depression

The function remains a mystery, may regulate food intake and body temperature.

*Epinephrin

cell body located in medulla projected to hypothalamus and thalamus and spinal cord, no function has been assigned to this agent

*Dopamine

-ultra short: in retina, in olfactory bulb

-intermediate length:

Tuberinfundibular system: prolactin

-long length: -negrostriatal involved in motor control

-mesocortical: from midbrain to limbic cortex and accumbens nucleus

Amphetamines which increase dopamine activity may lead to some schizophrenic symptoms

*Histamine

In the hypothalamus project to all parts of brain, its role is unknown.

Suggested role in: arousal, sexual behavior, blood pressure, drinking, pain threshold and regulation of the secretion of the pituitary gland

*AcetylcholineDistributed throughout CNS with high

concentration in the CC thalamus and basal ganglia

Involved in:-memory, motivation, perception and cognition-Olfaction-It has a relation with Alzheimer and nicotine-in basal ganglia Acetylcholine is an excitatory

transmitter while dopamine is an inhibitory transmitter

-Acetylcholine may have a role in parkinsonism-Acetylcholine may have a role in REM sleep

Other transmitters

Opioid, GABA (Chlorine conductance)

Excitatory amino acids __ Glutamate

|__ Aspartate