Nervous System: Stimuli and Reaction

Coordination Between Stimuli and Reaction: The Nervous System

• The nervous system enables quick and precise responses to stimuli.
• A goalkeeper's ability to react swiftly to an approaching ball relies on the nervous system.
• Sensory nerve cells transmit impulses from photoreceptors to the brain.
• The brain interprets the information and sends impulses to muscles in the arms and legs almost instantly.

Division of the Nervous System

• The nervous system consists of nerves made of nerve cells or neurons.
• There are approximately 100 billion neurons in the body.
• Most neurons are located in the brain and spinal cord.
• The brain and spinal cord form the central nervous system, protected by the skull and vertebral column, respectively.
• Neurons in the periphery form the peripheral nervous system, connecting the central nervous system to the rest of the body.
• Peripheral neurons link receptors to the spinal cord or brain, and the spinal cord or brain to effectors.
• Spinal nerves connect to or originate from the spinal cord, while cranial nerves connect to or originate from the brain.
• Long strands of nerves with interconnected nerve junctions, called sympathetic trunks, run along both sides of the vertebral column.

Structure and Function of the Nervous System

• The brain, part of the central nervous system, weighs between 1 and 1.5 kg.

• The brain is protected by three meninges and cerebrospinal fluid, which cushions against shocks.

• Deep grooves increase the brain's surface area, facilitating substance exchange between the brain and capillaries.

• The brain has three main parts: the cerebrum, cerebellum, and brainstem.

• The cerebrum and cerebellum are divided into two hemispheres: left and right.

• The hemispheres of the cerebrum communicate via the corpus callosum.

• The thalamus and hypothalamus are located beneath the corpus callosum.

• The thalamus coordinates sensory information.

• The hypothalamus mediates communication between the nervous and endocrine systems.

• The cerebrum consists of the white-colored medulla and the gray-colored cortex.

• The cerebral cortex processes information received through neurons in the medulla.

• The cerebral cortex transforms impulses from photoreceptors into images and impulses from auditory nerves into sounds.

• Impulses then travel from the cerebral cortex through the medulla to trigger bodily responses.

• Specific regions in the cerebral cortex analyze impulses, known as brain centers.

• Brain centers are classified as primary or secondary cortical centers.

• Primary motor centers control body movements.

• The size of the motor center corresponds to the fineness and mobility of the body parts.

• Primary sensory centers process sensations such as pain, heat, and cold.

• The sensitivity of an organ is proportional to the size of its sensory center.

• Secondary motor centers coordinate movements and automate skills

• Secondary sensory centers interpret sensations with recognition and memory.

• Each sense has its brain sensory center.

• The limbic system in the cerebrum is involved in emotion, motivation, and emotional memory.

• The limbic system regulates body temperature and appetite.

• Damage to the limbic system can disrupt feelings of hunger/satiety.

• The cerebellum, located beneath the cerebrum, makes up 10% of the brain but contains more neurons than the rest of the brain.

• The cerebellum refines and coordinates movements.

• It allows for implicit (unconscious) learning and coordinates balance.

• The cerebellum helps perform tasks using working memory.

• The thalamus, hypothalamus, and pituitary gland are situated between the cerebrum and brainstem.

• The thalamus acts as a sensory filter.

• The hypothalamus and pituitary gland are both hormone-producing glands.

• The hypothalamus modulates hormone production by the pituitary gland.

• The brainstem connects the spinal cord to the cerebrum and cerebellum and regulates vital functions such as heartbeat, respiration, and body temperature.

• Nerve fibers cross within the brainstem.

• If the brainstem malfunctions, brain death occurs.

• A significant portion of the parasympathetic nervous system originates from the brainstem.

Coordination in Stimulus Response

• The nervous system transmit impulses from receptors to effectors.
• It conducts impulses to muscles and glands.

Explore the nervous system's role in rapid responses to stimuli. Discover how sensory nerve cells transmit impulses to the brain, enabling quick reactions, such as a goalkeeper's save. Learn about the central and peripheral nervous systems and their components.