Human Nervous System: Brain Structures, Neurons, and Hormones

Major Brain Structures and Their Roles

Corpus Callosum

The bridge between the cerebral hemispheres is the corpus callosum.

Thalamus

Thalamus: Regulates communication between parts of the brain and relays sensory information; it also influences endocrine function.

Central Nervous System (CNS)

CNS: Consists of the brain and the spinal cord, covered by two protective layers (meninges).

Peripheral Nervous System (PNS)

PNS: The network of nerves that connects sensory receptors and effectors to the CNS; it links peripheral neurons to the central system.

Hippocampus

Hippocampus: Part of the limbic system important for long-term memory formation.

Hypothalamus

Hypothalamus: A primary regulator that connects nervous system activity to the endocrine system and helps control homeostasis.

Brainstem

Brainstem: Has different regions, including the medulla oblongata; it contains nuclei responsible for many vital functions.

Cerebellum

Cerebellum: With an outer layer of gray matter and inner white matter, it is responsible for movement coordination, balance, and motor learning.

Neuron Impulse Transmission

1. The nerve impulse travels from the dendrite to the end of the axon.
2. At the end of the axon there are many vesicles containing neurotransmitters; this is the pre-synaptic neuron.
3. The impulse causes the release of neurotransmitters into the space between the two cells (the synaptic cleft).
4. The neurotransmitters interact with receptors on the other side of the synapse; this is the post-synaptic neuron or cell.
5. The receptor in the post-synaptic cell responds; this is received by the dendrite of the next neuron or by an effector cell.

Pituitary Hormones and Actions

Directs the activity of other endocrine glands with a variety of hormones including:

• Oxytocin — to stimulate uterine contractions.
• Growth hormone — to control bone growth and elongation.
• Gonadotropic hormones (gonadotropins) — to act on the sex organs.

Types of Neurons

• Interneurons: Make up the central nervous system; they connect sensory and motor neurons.
• Sensory neurons: Carry messages from receptors to the central nervous system.
• Motor neurons: Carry messages from the central nervous system to effectors (muscles and glands).

Autonomic Nervous System

Sympathetic: Associated with situations of stress and increased energy demand.

Parasympathetic: Associated with relaxation, low energy expenditure, and tranquility.

Glands and Sex Hormones

Glands contribute to the development of sex organs and produce hormones such as testosterone and progesterone.