Nervous System: Functions, Circuits, Brain, Glands, and Hormones
Nervous System Functions
The nervous system performs several crucial functions:
- Receiving information transmitted by the sensory organs.
- Interpreting this information.
- Developing appropriate responses.
- Transferring orders to the effector organs.
- Coordinating the functioning of the body.
- Enhancing mental and intellectual functions.
- Responsible for emotions and feelings.
Nerve currents are transmitted by neurons, which possess a unique capacity to generate and transmit electrical signals. These signals travel from the dendrites to the axon. Neurons are not isolated; they establish functional connections called synapses. Synapses allow nerve impulses to pass from one neuron to another through specialized areas, typically at the end of the axon and a dendrite of the following neuron.
At the synapse, there is a narrow space known as the synaptic gap. At the end of the axon, tiny vesicles exist containing neurotransmitter substances. When a nerve impulse reaches the end of the axon, these vesicles rupture, releasing neurotransmitters into the synaptic gap. The nerve current is not continuous; it pauses momentarily before a new impulse begins. Synapses are control points of nervous transmission, and the intensity of transmission depends on the frequency and type of neurotransmitters released.
Nervous Circuits
- Divergent Circuits: Transmit signals from a single source to multiple organs.
- Convergent Circuits: Conduct nerve impulses from various locations to a single target.
Brainstem Components
Rakideo-Bulb (Medulla Oblongata)
This is the prolongation of the spinal cord. Pathways from the spinal cord and the brain pass through the medulla oblongata, where decussation (crossing over) occurs. This means the right side of the brain receives information from the left side of the body, and vice versa.
Brainstem Proper
The brainstem encompasses several brain regions located between the medulla oblongata and the brain. The hypothalamus, which controls many bodily functions, connects to the pituitary gland (hypophysis) within this region.
Cerebellum
Located at the back of the brain, the cerebellum consists of gray matter on the exterior and white matter on the interior. It receives information from the ear related to balance and coordinates motor commands sent by the brain to ensure precision of movement.
Brain (Cerebrum)
The cerebrum is the largest and most important part of the brain, composed of white matter on the exterior and gray matter on the interior, forming the cerebral cortex. The cerebral cortex exhibits numerous folds (gyri) and fissures (sulci), which can be shallow or deep. The brain is divided into two hemispheres connected by the corpus callosum. The functions of the brain include:
- Receiving information from sensory organs and processing it.
- Generating responses.
- Coordinating and controlling the nervous system.
- Supporting intellectual functions.
Glands and Hormones
- Pituitary Gland:
- Antidiuretic hormone: Decreases water loss in urine.
- Oxytocin: Contracts muscles during childbirth.
- Stimulating hormones: Regulate other glands.
- Growth hormone: Promotes overall growth.
- Adrenal Glands:
- Adrenaline (Epinephrine): Prepares the body for exertion.
- Steroids: Regulate metabolic processes and water balance in tissues.
- Aldosterone: Controls sodium and potassium concentration in the blood.
- Testes: Produce and maintain androgens (male sex hormones).
- Thyroid Gland: Thyroxine increases the intensity of metabolism.
- Parathyroid Gland: Parathyroid hormone regulates calcium and phosphorus levels in the blood.
- Pancreas:
- Insulin: Lowers blood glucose levels.
- Glucagon: Increases blood glucose levels.
- Ovaries:
- Estrogen: Similar function to androgens in males, but for female characteristics.
- Progesterone: Allows embryo implantation in the uterus.