Biological basis of behavior (new)

1. To be familiar with the different parts of a neuron, as well as it types and functions.

2. To be able to trace how neurons communicate with one another.

3. To be familiar with different parts of the nervous system and their functions

4. To identify parts of the endocrine system and their influence in human behavior

Neurons are the information-processing and information- transmitting element of the nervous system

They come in different shapes They may also be classified according to

their major functions

Sensory neurons- They gather information from the environment and transmit them to the brain

Motor neurons - Those that accomplish movement of the muscles

Interneurons - Can be found in the central nervous system; responsible for perceiving, learning, remembering, planning, and deciding among other important neural activities

Soma- Contains the nucleus and other parts that are responsible proving the life processes of the cell.

Dendrites- Tree-like structures that serve as the recipient of messages coming from the neighboring neurons.

Axon- The axon is a long slender tube, covered by a fatty insulator called the myelin sheath, that carries information from the cell body to the terminal button.

Bundles of axons constitute nerves

Terminal Buttons - Knob-like structures at the end of the axon’s twigs.

Action potential- brief electrical/ chemical event.

The transmission of the messages occurs in the synapse, a junction between the terminal buttons of the sending cell and a portion of the somatic or dendritic membrane of the receiving cell.

Terminal Buttons release chemicals known as neurotransmitters or transmitter substances

Neurotransmitters may be classified into two: excitatory or inhibitory

Multipolar neurons Bipolar neuron Unipolar neuron

Insert Picture (reflex)

Insert Picture (reflex)

A neuron fires an impulse when it receives signals from sense receptors that are stimulated by pressure, heat or light, or when it is simulated by chemical messages from adjacent neurons

If these signals exceed a minimum intensity, called the threshold, they trigger an impulse.

The impulse, called the action potential, is a brief electrical charge the travels down to the axon.

The neuron’s reaction is an all-or-none response, meaning they either fire or not.

A stronger stimulus cannot trigger a stronger or faster impulse, but they can trigger more neuron to fire.

When the Action potential reaches the terminals at an axons end, it triggers the release of chemical messengers, called neurotransmitters, onto the synapse – a gap between axons and dendrites of adjacent neurons.

These neurotransmitter molecules cross the synaptic gap and bind to the receptor site on the dendrites of the receiving neuron.

This allows electrically charged atoms to enter the receiving neuron and excite or inhibit a new action potential.

Dopamine influences movement, learning, attention, and emotion.

Serotonin affects mood, hunger, sleep, and arousal. Norepinephrine helps control alertness and arousal. Gamma-aminobyutric acid (GABA) inhibitory

functions and is sometime implicated in eating and sleep disorders.

Acetylcholine works on neurons in muscle action, learning and memory.

Endorphins are released in response to pain and vigorous exercise.

The nerve impulse can be excitatory; It prompts the adjacent neuron to fire.

An impulse can also be inhibitory; it prevents the adjacent neuron to fire

All-or-non law - An action potential either occurs or does not occurs, and is always in constant strength.

Rate law - A high rate of firing causes a strong muscular contraction and an intense odor causes a high rate of firing in the axon the serves the nose.

Saltatory conduction - action potentials are only conducted in a hopping fashion in the nodes of Ronvier

Reuptake - a rapid removal of neurotransmitter from the synaptic cleft by the terminal buttons

Enzymatic deactivation - enzymes destroy some neurotransmitter molecules into its constituents

The rate an axon fires is determined by the relative activity of the excitatory and inhibitory synapses on the soma and dendrites of that cell

The interaction of these activities is referred to as neural integration

If the activity of the excitatory synapses goes up, the rate of firing will go up. If the activity of inhibitory synapses goes up, the rate of firing will go down

Neuromodulators - chemicals released by neurons in larger amounts and diffused for the longer distances, modulating the activity of many neurons in a particular part of the brain

Hormones secreted by endocrine glands Hormones affect the activity of the cells

that contain specialized receptors, called target cells

Many neurons contain hormone receptors, thus influencing their activity

Anterior or Rostral- front end Posterior or Caudal – the tail Dorsal- the back surface Ventral- front surface Lateral-toward the side Medial- toward the midline Ipsilateral – same side of the body Contralateral- opposite sides of the body Cross section- slice transversely Horizontal section-slice parallel to the ground

(the brain) Sagittal section- slice perpendicular to the

ground and parallel to the neuroaxis

anterior

posterior

dorsal

dorsal

ventral

ventral

The brain is encased in a skull Floats in a pool of cerebrospinal fluid

(CSF) Chemically protected by the blood brain

barrier

Dura mater (the hard mother) Archnoid membrane – not found in PNS Pia mater ( pious mother) - contains

surface blood vessels and follows the surface convolution of the brain

Subarachnoid space - gap filled with cerebrospinal fluid

MAJOR DIVISION SUBDIVISION PRINCIPAL STRUCTURE

Forebrain Telencephalon Cerebrum/ Cerebral cortexBasal ganglia

Limbic System

Diencephalon Thalamus

Hypothalamus

Midbrain Mesencephalon Tectum/Tegmentum

Hindbrain Metencephalon Cerebellum

Pons

Myelencephalon Medulla Oblangata

Cerebrum, covered by the cerebral cortex

Limbic system

Basal ganglia

Two cerebral hemispheres Glia, cell bodies, dendrite, and

interconnecting axons of neurons Called the “gray matter” The cerebral hemisphere can be divided

into four areas

Lobes Regions / Areas

Frontal Lobe Primary motor cortex, Motor association cortex

Parietal Lobe Primary somatosensory cortex, somatosensory association cortex

Occipital Lobe Primary visual cortex, Visual association cortex

Temporal Lobe Primary auditory cortex, Auditory association cortex

With the exemption for the olfactory sense, all information from the body or the environment is sent to the primary sensory cortex of the contralateral (opposite) hemisphere.

Motor

The left hemisphere is concerned with analysis

The right hemisphere is specialized for synthesis

Two hemispheres are unified by the corpus callosum

Cerebrum, covered by the cerebral cortex

Limbic system

Basal ganglia

The amygdala is involved in the experience of emotion

The hippocampus is involved in learning and memory

Cerebrum, covered by the cerebral cortex

Limbic system

Basal ganglia

A collection of nuclei (groups of neurons of similar shape) deep within the forebrain

Involved in the control of movement

The thalamus The hypothalamus

Has two lobes Most neural input to the cerebral cortex is

received from the thalamus via projection axons

Thalamus

lateral geniculate

nucleus

medial geniculate nucleus

ventrolateral nucleus

Thalamus

lateral geniculate

nucleus

medial geniculate nucleus

ventrolateral nucleus

Cerebral Cortexprimary visual cortex

primary auditory cortex

primary motor cortex

The thalamus The hypothalamus

Controls the automatic nervous system and the endocrine system

Behaviors related to survival of the species, such as fighting, feeding and mating

Inferior colliculi - part of the auditory system

Superior colliculi - part of the visual system; involved in visual reflexes and reaction to moving objects

Reticular formation - plays role in sleep and arousal, attention, muscle tonus, movement and various vital reflexes

Periaqueductal gray matter - contains neural circuits that control sequences of movements such as fighting and mating.

From the red nucleus emerges one of two major fiber systems that bring motor information from the cerebral cortex and cerebellum to the spinal cord

The degeneration of neuron in the substantia nigra is responsible for Parkinson’s disease

Cerebellum Pons

The “little brain” Attached to the dorsal surface of the pons by

bundles of axons Facilitates standing, walking or performance of

coordinated movement, such as playing a musical instrument

Receives and integrates visual, auditory, vestibular and somatosensory information about individual muscle movements and modifies the motor outflow by exerting a coordinating and smoothing effect on the movements.

Contains portion of the reticular formation - important in sleep and arousal

Also contains a large nucleus that relays information from the cerebral cortex to the cerebellum

Medulla oblongata Contains part of the reticular formation As well as nuclei that controls vital function

such as regulation of cardiovascular system, respiration, and skeletal muscle tonus

A long, conical structure, approximately as thick as our little finger

Distributes motor axons Collects somatosensory information Functions independently - reflexive

control circuits

Housed by the vertebral column 24 individual vertebrae cervical (neck) thoracic (chest) lumbar (lower back) sacral and coccygeal portions

Spinal Nerves

Cranial Nerves - serve sensory and motor functions of the head and the neck region

Somatic nervous system - control movements of the muscles and to send sensory information from the sensory organs to the brain

Autonomic nervous system - control of smooth muscles, cardiac muscles and glands

Sympathetic nervous system – expenditure of energy from the reserves that are stored in the body

Thoracolumbar system

Parasympathetic nervous system - activities that are involved with the increase in the body’s supply of stored energy

Craniosacral system

Endocrine glands Processes that happen slowly, such as cell

growth, regulation of mood Produces and secretes or give off chemicals

- hormones Communicates messages, information and

instructions to other group of cells

Travel through the bloodstream to target cells (of body organs)

Target cells have receptors that latch only onto specific hormones

When hormone level reach a certain normal or necessary amount, further secretion is controlled by important body mechanisms - negative feedback system

The primary link between the endocrine and nervous systems

Controls the pituitary gland Releasing hormones -

signal the pituitary gland to secrete stimulating hormones

Somatostatin - causes the pituitary gland to stop the release of growth hormone

“Master gland” because it makes hormones that control several other endocrine glands

Can be influenced by factors such as emotions and seasonal changes

Hypothalamus relays these information anterior lobe , posterior lobe

Regulates the activity of the thyroid, adrenals, and reproductive glands

Growth hormone Prolactin Thyrotropin Corticotrophin Follicle-stimulating hormone Leutinizing hormone Endorphins Gonadotropic hormones

Antidiuretic hormone (vasopressin) Oxytocin

Shaped like a bowtie or butterfly Thyroxine , triiodothyronine - regulate

metabolism; body temperature and weight Iodine If iodine lacks in his/her diet, the thyroid

cannot make the hormones – Goiter Calcitonin - regulation (reduction) of

calcium level in the blood

Secrete parathyroid hormone, or parathormone

Parathormone - regulation (increase) of calcium level in the blood

Hypoparathyroidism - insufficient secretion of parathyroid hormone leading to increased nerve excitability.

Adrenal cortex

Adrenal medulla

corticosteroids such as cortisone - influences or regulates salt and water balance in the body; body’s response to stress, metabolism, the immune system and sexual development

Steroid hormones in three classes:

Mineralocorticoids maintain electrolyte balance

Glucocorticoids produce a long-term, slow response to stress by raising blood glucose level through the breakdown of fats and proteins

Sex hormones

Catecholamines, such as epinephrine - increases blood pressure and heart rate when the body experiences stress

Stimulated by the nerves from the eye Melatonin - a hormone that may help

regulate the wake-sleep cycle (circadian rhythm)

Secreted at night, when it is dark

Depressing the activity of the gonads Affects thyroid and adrenal cortex functions Seasonal affective disorder

Main source of sex hormones Testes located in the scrotum Ovaries, are located in the pelvis

Androgens most important of which is testosterone

regulate body changes associated with sexual development

supports the production of sperm

Produce eggs Estrogen - involved in the development of

female sexual features Progesterone - causes the uterine lining

to thicken in preparation for pregnancy Estrogen and progesterone - pregnancy

and the regulation of the menstrual cycle

Islets of Langerhans Glucagon - tells the liver to take

carbohydrate out of storage to raise a low blood sugar level

Insulin - tells the liver to take excess glucose out of circulation to lower a blood’s sugar level that’s too high

Diabetes mellitus