The Nervous System IIIAdv Biology 1-2

The Brain The brain consists of:

Cerebrum-has two hemispheres Cerebral cortex-outermost layer of the cerebrum,

has four lobes. Frontal lobe-reward, attention, short-term memory,

planning, motivation, consequences Parietal lobe-sensory integration, manipulation of

objects. Left hemisphere-symbolic (language and math). Right hemisphere-spatial relationships

Occipital lobe-processes visual information Temporal lobe-processes auditory input, language,

storing new memories, deriving meaning.

The Brain cont’dUnder the cerebrum is the limbic system.

Emotion, behavior, motivation, long-term memory, sense of smell. Thalamus-relays information from the senses

(except smell) to the cerebral cortex. Hypothalamus-links nervous system to the

endocrine system. Light, circadian rhythms, increases body

temperature, hunger. Amygdala-processing memory, decision-making,

emotional reactions (fear).

The Brain cont’d Hippocampus-turning short-term memories into

long-term memories. Olfactory bulb-sense of smell.

The Brain cont’dAll information passes through the brain stem

before entering the limbic system and the cerebrum.Brain stem contains the

Pons-relays sensory information between the cerebrum and cerebellum, sleep, autonomic functions

Medulla oblongata-autonomic functions, relays signals between the brain and the spinal cord.

Cerebellum-motor control and coordinated movements.

NeurotransmittersNeurotransmitters in the brain excite or

inhibit regions of the brain by binding to receptors.Excitatory neurotransmitters create action

potentials, making it easier for a neuron to fire.Inhibitory neurotransmitters make is harder to

create an action potential.

Neurotransmitters cont’dAcetylcholine (ACh)

In the CNS, ACh increases responsiveness to sensory stimuli and memory formation.

Epinephrine-released during fight or flight. In the PNS-increases heartbeat,

vasoconstrictor/vasodilator, breakdown of glycogen In the CNS-involved in memory formation, fear and

arousal.

Neurotransmitters cont’dDopamine-excitatory: attention, emotional

arousal, learning, memory, and reward. High levels reduce the size of the stimulus needed

to initiate a response. Selects and limits sensory information from the

thalamus.Seratonin-inhibitory and excitatory

Mood and behavior, appetite and sleep. Suppresses the appetite. Blocks dopamine

Neurotransmitters cont’dGABA (gamma-aminobutyric acid)-inhibits

other neurons, balances excitatory neurotransmitters. Reduce fear or anxiety created by over-excited

neurons.

Neurotransmitters cont’dWhen a neurotransmitter is no longer

needed, it is removed from its receptor.Pumps “vacuum” up the neurotransmitters,

returning them to the neuron that released them.

Some neurotransmitters are instead broken down in the synapse.

Until the neurotransmitters are removed from their receptors, the impulse will continue.