Nervous and Endocrine Systems: Functions
Nervous and Endocrine Systems
The nervous system’s purpose is to generate responses that provide protection. It is based on the body’s ability to respond to stimuli. Stimuli that humans and animals respond to may be of two types:
- Internal: Not visible (e.g., changes in temperature).
- External: Can be observed (e.g., responses to light).
The endocrine system complements the nervous system. It works via hormones produced by endocrine glands. These hormones travel through the blood to an organ or tissue to generate a response. Both systems share the goal of generating responses in the body. The endocrine system is slower because hormones must travel through the blood to reach the target organ, whereas the nervous system is fast because neurons are connected, generating a nerve impulse (neurotransmitters).
Central Nervous System
The central nervous system is divided into the brain and spinal cord.
Brain
The brain is divided into the brainstem, cerebellum, cerebrum, and diencephalon.
1. Brainstem
It is divided into three parts: the medulla oblongata, the pons, and the midbrain.
1A) Medulla Oblongata: Its function is to conduct sensory impulses to the brain and motor impulses from the brain to other pathways. It also houses centers for regulating heart rate, breathing, and swallowing.
1B) Pons: The pons is located between the medulla and the midbrain. Its function is to act as a control center for actions like laughing or crying.
1C) Midbrain: The midbrain is located above the pons. It connects, via fibers, the brainstem, cerebellum, and spinal cord to the brain. It also triggers pupil dilation.
2. Cerebellum
It is located at the base of the brain, below the occipital lobe, and is very small. Its functions are to control and manage large movements like walking. It also controls fine motor movements.
3. Cerebrum
It is the most important part of the central nervous system and the most developed part of the entire brain. It consists of three parts: the cerebral cortex, the central white matter, and the basal nuclei.
3A) Cerebral Cortex: A layer around the brain. It consists of a substance called gray matter, corresponding to the macrosoma of neuron bodies. The cortex has folds called convolutions, whose function is to interconnect many neurons, enabling humans to think and experience emotions.
3B) Central White Matter: Consists of neuronal axons.
3C) Basal Nuclei: These are small gray matter pellets. The brain has two divisions; each side corresponds to a hemisphere:
3-1) Right Hemisphere: This is the sensitive hemisphere, related to spatial orientation, artistic and creative abilities, emotions, and so on.
3-2) Left Hemisphere: This hemisphere is responsible for calculation and critical thinking, enabling mathematical and verbal comprehension. It also plays a role in the development of short- and long-term memory. The control by the brain hemispheres is crossed; the right hemisphere controls the left half of the body, and the left hemisphere controls the right half.
4. Diencephalon
4A) Thalamus: Any information leading to the brain is overseen by the thalamus. The thalamus contains centers for swallowing, contact pressure, and the perception of pain.
4B) Hypothalamus: This is the center for homeostasis (regulating the body’s balance). It controls blood pressure, body temperature, glucose concentration, and heart rate.
5. Spinal Cord
A nerve cord that lies from the foramen magnum (neck) and runs through all the vertebrae. Its purpose is to conduct sensory impulses to the brain and also drive motor impulses from the brain to the body. It is the center for reflexes, enabling rapid responses (e.g., the patellar reflex).
Peripheral Nervous System
Consists of all the nerves and ganglia that are throughout our bodies but are concentrated in the inguinal, maxillary, and axillary regions. The function of this system is to transmit all sensations to the central nervous system.
A) Somatic Nervous System: Responsible for receiving sensory signals carried to the brain and conveying motor responses to skeletal muscles. This system is voluntary, carrying the brain’s responses to the extremities.
B) Autonomic Nervous System: This system is involuntary. It is responsible for bringing information from the viscera to the brain. (Viscera = membranous layer covering the organs; it carries motor responses from the brain to smooth muscles). The sympathetic nervous system prepares the body for any changes that generate excitement, impacts, etc. The parasympathetic nervous system restores the body and keeps it in a resting state.