Biopsychology: The Nervous System

• Biopsychology studies the biological bases of behavior and mental processes.

The Nervous System

• A specializedCell network within the body, is the internal communication system.
• It uses electrical signals for communication.
• Its functions include processing information, responding to the environment, and coordinating bodily functions.
• It has two subsystems: the central nervous system (CNS) and the peripheral nervous system (PNS).

Central Nervous System (CNS)

• The brain and spinal cord make up the CNS.
• The cerebral cortex is the brain's 3mm thick outer layer, divided into two hemispheres.
• The spinal cord relays messages to and from the brain and handles reflex actions.

Peripheral Nervous System (PNS)

• The PNS transmits messages between the CNS and the body through neurons.
• The PNS consists of the autonomic nervous system and the somatic nervous system.
• The autonomic nervous system controls vital functions such as heart rate.
• The somatic nervous system controls muscle movement and sensory input.

The Endocrine System

• This system communicates through hormones released into the bloodstream.
• It instructs glands to release hormones that travel to target organs.
• The thyroid gland produces thyroxine, which affects cells in the heart and increases metabolic and growth rates.
• The pituitary gland controls hormone release from other endocrine glands, acting as a 'master gland'.

Fight or Flight Response

• When a stressor is perceived, the hypothalamus activates the pituitary gland and the sympathetic branch of the autonomic nervous system.
• The adrenal medulla releases adrenaline into the bloodstream, causing physiological changes like increased heart rate.
• This process is an immediate, automatic response.
• After the threat passes, the parasympathetic state returns, decreasing breathing and heart rate (rest and digest).

Neuron Structure and Function

• There are three types of neurons: sensory, relay, and motor.
• The cell body contains the nucleus (genetic material).
• Dendrites carry nerve impulses to the cell body.
• The axon carries impulses away from the cell body.
• The myelin sheath insulates the axon and speeds up transmission.
• Nodes of Ranvier facilitate faster transmission by allowing impulses to 'jump'.
• Terminal buttons communicate with the next neuron across the synapse.

Neuron Location

• Sensory neurons are located outside the CNS in ganglia.
• Relay neurons are located in the brain and visual system.
• Motor neurons are in the CNS and have long axons in the PNS.

Electrical Transmission

• A neuron is negatively charged in its resting state.
• Upon activation by a stimulus, it becomes positively charged, leading to an action potential and an electrical impulse down the axon.

Synaptic Transmission

• Neurons communicate by sending chemical messages (neurotransmitters) across the synapse.
• An electric impulse triggers the release of neurotransmitters from synaptic vesicles.
• Neurotransmitters cross the synaptic gap and bind to postsynaptic receptor sites, converting the chemical signal back into an electrical impulse.
• This process is unidirectional.
• Each neurotransmitter has a specific structure to fit perfectly into its corresponding postsynaptic site.

Neurotransmitters: Excitatory and Inhibitory

• Excitatory neurotransmitters, such as adrenaline, increase the neuron's positive charge and the likelihood of firing.
• Inhibitory neurotransmitters, such as serotonin, make the receiving neuron more negatively charged and less likely to fire.

Summation

• Whether a postsynaptic neuron fires depends on the combined effect of excitatory and inhibitory inputs.
• If the net effect is inhibitory, the neuron is less likely to fire; if excitatory, it's more likely to fire.
• An action potential is triggered only if the total excitatory input reaches a threshold.