Neurons Generate Electricity and Release Chemicals

Chapter3

Neurons (Generate electricity and release chemicals)

a cell body(soma), dendrites and an axon

• Cell body:1. keep the neuron alive

                           2. nucleus contains the genetic information that determines how the    neuron develops and functions

• Dendrites: collect messages from neighbouring neurons and send them on to the cell body
• Axon: conduct electrical impulse away from the cell body to other neurons, muscles or glands.
• Glia cell：1. Surround neurons and hold them in place

                2.manufacture or transport nutrients

                3. form the myelin sheath

                4. absorb toxins and waste materials that might damage neurons

                5. protect the brain from toxin

6. modulate the communication among neurons

• Type：1. Sensory neurons-carry input message from sense organs to the spinal cord and brain

2. Motor neurons-transmit output impulses from spinal cord and brain to muscles and organs.

3. Interneurons-connective and associated function

Neurotransmitter

Glutamate (+): the mechanism involved in learning and memory

GABA (-): motor control and the control of anxiety and arousal

Acetylcholine-ACH (+): memory and muscle movement -Alzheimer’s disease

Dopamine (+/-): motivation, reward, feelings of pleasure, voluntary motor control and control of thought processes-Parkinson’s disease (undersupply)

Serotonin (-): influence mood, eating, sleeping and sexual behavior-depression

Endorphin (-): reduce pain and increase the feeling of well-being

The nervous system

• Central nervous system

The spinal cord- spinal reflexes can be triggered at the level of the spinal cord without any involvement of brain

           Discover the brain:

           1. Neuropsychological tests---measure verbal or non-verbal behaviors that affected by particular types of brain damage

           2. Destruction and stimulation technique---transcranial magnetic stimulation or TMS-a magnetic coil placed close to head to generate a magnetic field that disrupt activity in the brain

           3. EEG-place larger electrodes on the scalp to measure activity of large groups

           4. CT (structure)- X-ray takes pictures of narrow slices of brain and then analyze the slices and create pictures of interior from different angles

           5. PET (activity)- glucose is injected and tell how active particular neurons are by measuring the amount of radioactive glucose that accumulate in them.

           6. MRI (structure and activity)-detailed images based on how atoms in living tissue respond to a magnetic pulse (e.g. alter the magnetic field and atoms absorbed the magnetic energy emit a small electrical voltage)

           7. fMRI- watch live presentations as different regions of the brain light up when given tasks to perform

• Peripheral nervous system
• P-Somatic nervous system

Sensory neurons that from eyes and ears and other sensory receptors

Motor neurons that from~ to muscles that control voluntary movements

• P-Automatic nervous system

Concerned with involuntary functions like respiration, circulation, digestion and many aspects of motivation, emotional behavior, stress responses.

• A-sympathetic nervous system (act like a total unit)

activation or arousal function-mobilize body to confront stressor

• A-parasympathetic nervous system (unit-affect one or few organs at a time)

slow down body process and maintain or return to a state of rest

homeostasis

some act needs a coordinated sequence

The brain

• The hindbrain

The medulla (first structure after leaving the spinal cord):

1. Support vital body functions like heart rate and respiration

2. a two-way thoroughfare for all the sensory and motor nerve tracts coming up from the spinal cord and descending from the brain

Pons (just above the medulla):

1. Bridge carrying nerve impulse between higher and lower level of the nervous system
2. Contain motor neurons that control the glands and muscles of the face and neck
3. Vital function like heart rate and respiration

           The cerebellum (just above the pons)

1. Muscular movement coordination (timing and coordination of specific motor movements)
2. Learning and memory

• The midbrain (above the hindbrain)

1. Sensory portion contains relay centers for the visual and auditory systems
2. Motor neurons that control eye movements

Reticulum (buried within the midbrain extending from the hindbrain up into the lower portion of forebrain)

1. Reticular formation:

1) alert higher brain that messages are coming and then either blocking or allowing them to go forward.

2) ascending part which send input to brain

3) descending portion through brain can admit or block out sensory input

4) consciousness, sleep and attention

• The forebrain (or cerebrum)

The thalamus (above the midbrain):

1. Organize inputs from sense organs and routes them to the appropriate areas of the brain.
2. The visual, auditory and body senses (balance and equilibrium) all have major relay stations in it
3. Recently, it functions as an active, dynamic filter selecting what information to the brain

Basal ganglia (surrounding and enveloping the thalamus)

1. Voluntary motor control (initiate voluntary movement)-PARKINSON’S disease

Hypothalamus (under the thalamus)

1. Control basic biological drives including sexual behavior, temperature regulation, eating, drinking, aggression and the expression of emotion
2. Have important connection with endocrine system (pituitary gland is the master gland) which controls hormonal secretions
3. The brain area critical for motivation and reward for drugs of abuse and food (dopamine actions in nucleus accumbens)

The limbic system (lying deep within the celebral hemisphere)

1. Helps to coordinate behaviors needed to satisfy emotional and motivational urges in hypothalamus
2. Helps to carry out organized and goal-directed sequences

Hippocampus (form and retrieve memory)

Damage-forget recent event and cannot transfer information from short-term memory to long-term memory

Amygdala

1. organize emotional response pattern, particularly those linked to aggression and fear
2. Electrically stimulating some areas causes animals to snarl and aggressive, whereas stimulating other areas result in a fearful ability to respond aggression, even in self-defence.
3. Produce emotional responses without brain knowing.

The cerebral cortex (essential for a human quality of living)