THE HUMAN NERVOUS SYSTEM

Nervous Tissue

Controls and integrates all body activities within limits that maintain life

three basic functions of nervous tissue

-sensing changes with sensory receptors

-fullness of stomach or sun on your face

- interpreting and remembering those changes

Central Nervous System (CNS)

• Includes: The brain and spinal cord

• Function: Acts as the control center for processing and sending signals throughout the body.

Peripheral Nervous System (PNS)

• Consists of cranial and spinal nerves.

• It serves as the communication line between the CNS and the rest of the body.

Sensory (Afferent) Division

• Carries information from receptors to the CNS

• Includes somatic and visceral sensory nerve fibers.

feeling pain when touching something hot

Autonomic nervous system

Visceral motor (Involuntary

Conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands

Sympathetic Division

("Fight or Flight") → Prepares the body for action (increases heart rate, breathing, energy use)

Parasympathetic Division

Conserves energy and promotes relaxation (slows heart rate, aids digestion)

Motor (Efferent) Division

• Carries instructions from the CNS to muscles and glands. (responsible for sending instructions from the central nervous system (CNS) )

• Includes motor nerve fibers.

Brain (CNS)

• The brain processes sensory stimuli information (Somatic & Autonomic).

• It controls voluntary movements (Somatic - execution of motor responses).

• It also regulates involuntary functions (Autonomic - homeostatic mechanisms like heart rate and digestion).

Spinal cord (CNS)

• Acts as a communication bridge between the brain and the body by serving as a pathway for sensory and motor functions.

• Initiates reflexes from the ventral horn (Somatic - voluntary movements like pulling your hand away from heat) and lateral horn (Autonomic - involuntary responses like pupil dilation).

Nerves (PNS)

• These are fibers of sensory and motor neurons, transmitting signals between the CNS and the body.

• Somatic Nerves → Control voluntary movements (e.g., moving your arm).

• Autonomic Nerves → Control involuntary functions (e.g., heartbeat, digestion).

Ganglia (PNS)

Reception of sensory stimuli by dorsal root and cranial ganglia (somatic/automatic)

Relay of visual motor responses by autonomic ganglia

• Digestive Tract (ENS)

• Functions independently of the brain and spinal cord, managing digestion autonomously.

  • This aligns with the Autonomic Nervous System, specifically the Parasympathetic Division, which controls digestion and relaxation.

Somatic Nervous System

(Voluntary Control) → Controls skeletal muscle movements.

Autonomic Nervous System

(Involuntary Control) → Regulates internal organs (heartbeat, digestion, breathing).

Cranial Nerves

Nerves that go from your brain to your eyes, mouth, ears, and other parts of your head

Central Nerves

Nerves that are located in your brain and spinal cord.

Peripheral Nerves

Nerves that extend from your spinal cord to your arms, hands, legs, and feet.

Autonomic Nerve

Nerves that go from your spinal cord to your lungs, heart, stomach, intestines, bladder, and sex organs

Cerebrum

The largest part of the brain, responsible for thinking, voluntary movements, perception, memory, and emotions.

Frontal Lobe

Involved in decision-making, problem-solving, movement, and personality.

Parietal Lobe

Processes sensory information like touch, temperature, and pain.

Occipital Lobe

Responsible for vision and visual processing.

Cerebellum

Controls balance, coordination, and fine motor movements.

Thalamus

A relay station for sensory information, sending signals to the appropriate brain areas.

Hypothalamus

Regulates body temperature, hunger, thirst, sleep, and emotions.

Pineal Body (Gland)

• Produces melatonin, regulating sleep-wake cycles.

Olfactory Bulb

• Processes smell signals from the nose.

Pituitary Gland

Known as the "master gland," it controls hormone production and regulates bodily functions.

Pons

• A part of the brainstem that helps control breathing, sleep, and communication between different brain parts.

Reticular Formation

Regulates consciousness, sleep-wake cycles, and alertness.

Medulla Oblongata

Controls vital functions like heart rate, breathing, and digestion.

Meninges

Three protective layers surrounding the brain and spinal cord

Cerebrospinal Fluid (CSF)

• Cushions the brain, providing protection and nutrient transport.

Ventricle

A cavity in the brain filled with cerebrospinal fluid, helping to protect and nourish the brain.

Primary Motor Cortex

Controls voluntary movements of muscles.

Premotor Cortex

Helps in planning and coordinating voluntary movements

Central Sulcus

A groove in the brain that separates the frontal and parietal lobes.

Primary Somatosensory Cortex

Processes sensory input like touch, temperature, and body position (proprioception).

Sensory Association Areas

Integrates sensory information for better perception and response.

Visual Association Areas

Responsible for complex visual processing and interpretation.

Primary Visual Cortex

– Processes basic visual information like colors and shapes.

Wernicke’s Area

• Important for understanding language and speech.

Auditory Association Areas

Helps interpret sounds and speech.

Primary Auditory Cortex

– Processes sounds, including speech and music.

Limbic Association Cortex

Involved in emotions, learning, and memory

Olfactory Cortex

– Processes smells and olfactory sensations.

Broca’s Area

– Controls speech production and language expression.

Prefrontal Association Areas

– Involved in decision-making, personality, voluntary movement planning, and thought processes.

• Parietal Lobe

• • Touch perception (processes sensory information from the skin)

  • Movement control (helps coordinate voluntary movements)

  • Manipulation of objects (spatial awareness and hand-eye coordination)

Frontal Lobe

• Voluntary movement (controls motor functions)

• Planning (decision-making and goal setting)

• Intellect (associated with intelligence and reasoning)

• Problem-solving (critical thinking and logical reasoning)

• Abstract reasoning (thinking beyond concrete information)

Occipital Lobe

• Visual reception (processes visual information from the eyes)

• Local orientation (recognizes the position of objects in space)

• Shape perception (identifies shapes and visual patterns)

Temporal Lobe

• Long-term memory (stores and retrieves past experiences)

• Speech comprehension (understanding spoken and written language)

• Object perception (recognizing and identifying objects)

• Face recognition (helps in identifying familiar faces)

• Hearing (processes auditory information)

Cerebral cortex

Thin layer of gray matter that constitutes the outermost portion of cerebrum, contains 75% of all neurons in the nervous system