Central Nervous System structures and functions

• The central nervous system is composed of the brain and spinal cord.
• Association or interneurons form a network of communication between brain areas.
• Brain study is organized according to embryonic divisions: forebrain, midbrain, and hindbrain.

Central Nervous System Functions

• Receives input from sensory neurons.
• Directs the activity of motor neurons.
• Association neurons integrate sensory information, directing appropriate responses to maintain homeostasis and respond to the environment.
• Humans use learning and memory to modify behaviors.

Forebrain: Cerebrum

• The cerebrum handles higher mental functions.
• It's the largest part of the brain, characterized by many synapses.
• Cerebrum consists of temporal, parietal, frontal, occipital, and insula lobes.
• The cerebral cortex is the outer gray matter.
• Cerebral hemispheres are divided into lobes.
• The corpus callosum is a bundle of nerves connecting cortex layers of the left and right hemispheres, facilitating communication between them

Limbic System: Emotions

• Emotions are controlled by the limbic system, influencing emotion, memory, and behavior.
• The limbic system is physically linked to the thalamus and hypothalamus.
• Aggression areas are in the amygdala and hypothalamus.
• Fear is linked to the amygdala and hypothalamus.
• Hunger/satiety is related to the hypothalamus.
• Sex drive involves the whole system.
• Goal-directed behavior is controlled by reward/punishment mechanisms.
• Few connections exist between the cerebral cortex and limbic system, thus limiting conscious control over emotion. The hypothalamus and limbic system work together in neural bases of emotion.

Hippocampus

• Part of the medial-lobe structure, responsible for memory formation and retrieval.
• It forms cognitive maps for mental models of the world.
• Stress and emotion can affect it through the limbic system.
• Contains cortisol receptors affecting short-term memory.

Amygdala

• Part of the medial-lobe that combines different sensory inputs.
• Memory and emotion combine if emotion is strong enough.

Forebrain: Diencephalon

• Connects cerebrum to the rest of the nervous sytem.
• The thalamus relays sensory information (except smell). It directs traffic, prioritizing information flow. Cerebrum sends info to thalamus-motor commands.
• The epithalamus regulates circadian rhythms and contains choroid plexus + pineal gland. It has a gaba-inhibitory role to limit senses and promote sleep.

Forebrain: Hypothalamus

• A major diencephalon region, command center for endocrine.
• Connects CNS and endocrine systems.
• Influenced by higher brain centers, it regulates the pituitary gland.
• Essential for homeostasis, controlling survival needs like eating, drinking, and body temperature.
• Produces and releases antidiuretic hormone (ADH) and Oxytocin

Midbrain

• Connects cerebrum and cerebellum.
• Located between thalamus and pons.
• Functions in motor control, maintaining cerebrum to cerebellum connections.
• Dopaminergic neurons project to basal nuclei and limbic system, releasing dopamine.
• Neurons going to the limbic system, hippocampus, and amygdala link the reward system, a key area for drug addiction studies.
• Dopamine, released in the nucleus accumbens after consuming certain addictive drugs, is a neurotransmitter/hormone linked to good feelings.

• The brainstem & spinal cord communicate a physical or autonomic nervous response through heart rate, and memory of experiences are stored in the hippocampus.
• Opioid neurotransmitters mediate addiction and reward.
• Beta-endorphin acts on multiple opioid receptors to block pain transmission.
• Opioids produce euphoria and mediate reward pathways through release of endorphins.

Hindbrain: Cerebellum & Pons

• Transmit sensory and motor information to the brain.
• Complex motor skills and coordinates movements/motor learning are controlled here.
• Receives data from muscles, joints (proprioceptors), skin, and eyes.

Medulla Oblongata

• Autonomic functions regulate cardiovascular and respiration.
• All ascending and descending tracts between the brain and spinal cord pass through the medulla.

Neurotransmitters

• Glutamate is excitatory.
• Dopamine is excitatory.
• GABA is inhibitory.
• Major neurotransmitters include: Acetylcholine, Beta-endorphin, Dopamine, Gamma-aminobutyric acid (GABA), Glutamate, Norepinephrine, and Serotonin.

PNS Nerves: Spinal Nerves

• Spinal nerves have 31 pairs.
• Nerves separate near spinal cord: Sensory fibers passs through the dorsal root, and motor fibers pass through the ventral root.
• Spinal nerve pairs:
  • 8 Cervical
  • 12 Thoracic
  • 5 Lumbar
  • 5 Sacral
  • 1 Coccygeal

Reflex Arc

• Reflex responses to stimuli are a multi-step process.
• A stimulus activates sensory neuron receptors.
• Signal travels along the afferent neuron to the central nervous system.
• The interneuron connects to the motor neuron.
• The motor neuron transmits the impulse to the effector organ.

Types of Reflex Arcs

• Some reflexes require association areas and brain interneurons.
• Examples include: crossed extensor reflex
• Muscle Stretch Reflex links afferent and efferent neurons directly together.
• Examples include: Knee-jerk reflex

Explore the key components of the central nervous system, including the cerebrum, cerebellum, and brainstem. Understand the roles of association neurons, neurotransmitters like dopamine, and brain structures such as the hypothalamus and hippocampus.