The Nervous and Endocrine Systems and the Sensory and Motor Neurons

Psychology /Nursing
Nervous System
CBB062
Dr. Felix Ikie
TASK 1: AC. 1.1-ANSWER
Diagram 1: The annotated flowchart that depicts parts of the nervous system
Flight-or-flight response in the nervous and endocrine systems
The nervous and endocrine systems work in coordination during the flight-or-flight response. Different parts of the nervous system execute specific functions. When an imminent threat or danger is perceived, the sympathetic nerve fiber activates the autonomic nervous system (ANS) (Hau et al., .2020). The activation triggers the endocrine system to release the adrenaline hormone that is responsible for the fight-or-flight response. The primary function of adrenalin is to activate a rapid response. The adrenaline glands secrete adrenalin, which together with non-adrenaline prepares the body's defense mechanism to deal with the imminent threat (Kandel & Schwartz, 2012). Adrenaline triggers a sudden decline in blood pressure, abrupt emotional change, and a decline in blood glucose. The flight-or-flight response manifests through an abrupt increase in heart rate, anxiety, high perspiration, body tremor, and glycogenolysis.
The breakdown in glycogen by the liver releases the energy that the body needs to execute a flight-or-flight response. The endocrine and nervous systems collectively control hormonal responses that activate increased corticotrophin and cortisol release that cause a prolonged flight-and-flight response (Estomih et al., 2012). Besides the increased release of cortisol and adrenal cortex, the flight-or-flight response can also trigger the secretion of high levels of glucagon and catecholamine by islet cells (pancreas) and adrenal medulla respectively. The fight-or-flight response activates the alpha-adrenergic receptors to constrict blood vessels, uterine muscles and may dilate the eye pupils (McCraty et al., 2017). However, the activation of beta-receptors causes a sudden increase in heart rate that triggers cardiac constriction. Still, the response dilates the bronchi and blood vessels.
The flight-or-flight response happens in different situations such as when a driver slams on the car breaks to avoid an accident. The second example is when a person suddenly encounters a growling dog. Similarly, when a walking person almost steps on a snake, the immediate response is a flight-or-flight response. The immediate reaction is to take off and run away from the dog. The fight-or-flight response activates the adrenal glands to secrete large quantities of epinephrine (adrenaline) which increases the heart rate, cardiac output, muscle constriction among other nervous system responses (Hau et al., .2020). In response, the endocrine system releases cortisol and adrenal cortex, glucagon, increased secretion of epinephrine.
TASK 2: AC.2.1
* The structure and features of a neuron
Diagram 1: Annotated diagram of a neuron
Source: (Nervous System, 2020).
A typical neuron comprises the nucleus, dendrites, cell body, axon, myelin sheath, the node of Ranvier, axon terminal, and the Schwann cell. The structure of the neuron enables it to transmit and receive electrical throughout the body (Nervous System, 2020). Neurons work together with glial cells that provide protection and insulation.
Source: (Human body, 2020).
1 Dendrites- Collect signals. These are specialized parts of a neuron that receive chemical impulses transmitted by the axon terminal of neighboring neurons. Still, they convert chemical impulses into electric signals before transmitting them inward toward the cell body (Nervous System, 1996).
2 Cell body/Soma- It's the core of the neuron that houses genetic information while maintaining the neuron's structure. Also, it generates energy that initiates cell activities and comprises specialized organelles.
3 Axon-Facilitates inter-neuron communication through the intercellular transmission of impulses
4 The node of Ranvier- It facilitates rapid transmission of nerve impulses and electrical signals
5 Axon terminal- Release neurotransmitters within the presynaptic cell which transmits substances to the synaptic cleft, that sits between the terminals and the dendrites of the neighboring neurons.
6 Schwann cell-Its function is the myelination of the axons in the peripheral nervous system (PNS). Myelin is a specialized fatty layer that insulates the axon to increase salutatory conduction in the neuron that wraps around the single axon (Human body, 2020).
7 Myeline Sheath- The primary function of the myelin sheath is to protect the nerves or the nervous system from electrical signals conducted by neighboring neurons. Still, it accelerates the transmission of impulse within the axon.
8 Nucleus-The nucleus stores the genetic information ij form of coded strings also referred to as deoxyribonucleic (DNA) and works alongside dendrites to enable signal transmission (Nervous system, 1996).
AC.2.2
* Motor and sensory neurone diagrams, similarities & differences
* DIFFERENCES: SENSORY vs. MOTOR NEURONS
Source: Nervous System, 1996.
DIFFERENCES: SENSORY vs. MOTOR NEURONS
Sensory Neuron

Motor Neuron

Neurons that transmit impulse from sensory organs to the CNS are called sensory neurons

A neuron that conducts motor impulse from the CNS to effectors are called motor neurons

They are situated in the dorsal root or ganglion in the spinal nerve

They are located in the ventral root ganglion, within the spinal cord.

Sensory neurons are unipolar

Motor neurons are multipolar

Has short axon

Has a long axon

Adults have over 10 million

Adults have half a million

Located in sensory organs e.g. eyes, skin, ears, tongue, and nose

Located in muscles and glands

Carries signals from outer/peripheral parts to CNS

Carries signals from the CNS to outer parts i.e muscles and glands

Has long dendrons

Has short dendrons

Source: Estomih et al., 2012; Human Body, 1996.
SIMILARITIES: SENSORY vs. MOTOR NEURONS
1 Both motor and sensory neurons comprise cell bodies
2 Both comprise dendrites linked to neurons
3 They share a similar function of transmitting action potential from one organ or part of the body to another.
TASK 3: AC.2.3
* Actions that take place during action potential in a myelinated neuron.
A neuron receives impulse or signal input from other neurons. The neural transmission occurs in a chemical referred to as a neurotransmitter. If the impulse is strong, the neuron transmits it to downstream neurons (Ann, 1999). Electrical signal transmission within a neuron (unidirectional, dendrite to axon) is facilitated by the opening and closing of the gated ion channels. The opening and closing of the gated channels can temporarily trigger a reversal of the resting membrane's potential to create an action potential (Kandel & Schwartz, 2012). While the action potential moves downstream towards the axon, a change in polarity is triggered. Immediately the signal reaches the axon terminal, it triggers a multi-neural stimulus.
Figure 2: The Creation of Action Potential
(Source: Kandel & Schwartz, 2012).
The action potential in a myelinated neuron goes through five steps.
STEP 1:
A stimulus is released from the sensory cell that causes the target cell to depolarize and move closer to the action potential.
STEP 2:
When the excitation threshold is hit, Na+ channels will open to allow membrane depolarization.
STEP 3:
During the peak action potential, K+ channels open and starts exiting the cell while causing the Na+ channels to shut.
STEP 4:
The membrane reaches hyperpolarization when K+ ions continue to move from the cell. The hyperpolarized membrane is dormant and cannot fire (refractory period).
STEP 5:
The K+ channels shut while the Na+/K+ transmitters go back to the resting position.
Action Potential in myelinated neuron
Action potentials are regarded as all-or-nothing action since the neurone depolarizes at the threshold potential. Once depolarization is completed, the cell will reset its membrane voltage to resting potential. The Na+ channels shut, heraldin...