Nervous System: Neurons and Impulses

• The nervous system collects and processes internal and external environmental information, and then generates a response.
• A stimulus is environmental information that causes an organism to respond.
• Impulses are electrical signals used to carry messages.
• Neurons are nerve cells that transmit impulses.
• The Central Nervous System (CNS) comprises the brain and spinal cord and processes information to create responses.
• Peripheral Nervous System (PNS) carries responses to muscles, glands, and other tissues.

Neuron Types

• Sensory neurons carry impulses from sense organs to the CNS.
• Motor neurons carry impulses from the CNS to the PNS.
• Interneurons process information and send commands to other interneurons or motor neurons.

Nervous System Evolution

• Nerve nets feature simple neurons in net-like arrangements with limited specializations.
• Nerve cords involve interneurons grouped in a ring that stretches out to appendages.
• Ganglia are structures where interneurons connect.
• Cephalization is the concentration of sensory neurons and interneurons in a "head."
• Brains are cerebral ganglia with further specialization.
• Chordates possess a spinal cord, resulting in a highly developed nervous system with interconnected interneurons, sensory, and motor neurons.

Central Nervous System Details

• The CNS is composed of the brain and spinal cord.
• It's protected by the skull and vertebral column.
• Distinct brain regions are linked to specific sensations.
• Muscle commands originate in brain regions
• The spinal cord connects the brain to the rest of the body

Peripheral Nervous System Details

• The PNS consists of muscles, glands, and other tissues.
• Sensory receptor cells in the PNS gather information and send impulses to the CNS through sensory neurons.

PNS Divisions

• The Somatic system regulates skeletal muscle movement and reflexes.
• Reflexes are rapid, automatic responses generated by impulses that bypass the brain.
• The Autonomic system regulates activities without conscious control.
• Rapid heart rate and sweat production are examples.
• The Sympathetic system prepares for intense activity, triggering "fight or flight".
• The Parasympathetic system promotes "rest and digest" responses.

Cerebrum

• The cerebrum is the region of the brain that interprets sensory information and determines a response.
• It is responsible for learning, memory, and conscious thought.

Lobes of the Brain

• The frontal lobe controls thinking, planning, organizing, problem-solving, and short-term memory.
• The parietal lobe interprets sensory information like texture and temperature.
• The temporal lobe processes smell, taste, and sound and plays a role in memory storage.
• The occipital lobe processes images from the eyes and connects them to stored memories.

Spinal Cord

• The vertebral column protects the spinal cord.
• Intervertebral disks between vertebrae provide cushioning.
• These disks are composed of a gelatinous substance called nucleus pulposus.
• Compression of these disks occurs during the day.
• Muscle strength loss with age can contribute to spine curvature.

Medulla Oblongata Functions

• Relays sensory information to the thalamus and brainstem
• Contains autonomic centers for regulation of vital signals and digestive system activities.
• Controls the functioning of many internal organs.
• The Optic lobes are involved in the brains vision (Purple).
• The Olfactory bulbs are involved in the brains sense of smell (Pink).

Meninges

• Meninges are protective membranes surrounding the brain and spinal cord
• Pia mater is the inner layer.
• Arachnoid layer is a web-like structure filled with cushioning fluid.
• Dura mater is the tough outer layer.

Pons Functions

• Relays sensory information to the cerebellum and thalamus
• Contains subconscious somatic and visceral motor centers
• Sets the body’s level of alertness when waking up.
• Manages pain signals.